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Panitumumab (Vectibix)

Web Resources: Panitumumab (Vectibix)
Latest Research Publications

Web Resources: Panitumumab (Vectibix) (6 links)


Latest Research Publications

Zhang H, Zhang X, Wang J, et al.
Comparison of high-resolution melting analysis, Sanger sequencing and ARMS for KRAS mutation detection in metastatic colorectal cancer.
Clin Lab. 2015; 61(3-4):435-9 [PubMed] Related Publications
BACKGROUND: Treatment of metastatic colon carcinoma with the anti-epidermal growth factor receptor antibody cetuximab/panitumumab is reported to be ineffective in KRAS-mutant tumors; therefore, it is necessary to perform KRAS mutation analysis before cetuximab or panitumumab treatment is initiated.
METHODS: This study was designed to compare and evaluate the efficacy of three different methodologies--high resolution melting (HRM), Sanger sequencing, and Amplification Refractory Mutation System (ARMS)--for KRAS mutation detection in a clinical setting.
RESULTS: In total, 55 samples from patients with metastatic colorectal cancer were analyzed. Compared to Sanger sequencing, good consistency was found between the results of the ARMS (Kappa = 0.839) and HRM (Kappa = 0.839). The sensitivities of the methods were compared after a consensus was reached: if two of the three methodologies showed a similar result, it was considered as the consensus result. The frequency of KRAS mutations in our population was 34.5%, and discordant findings were observed in five samples. No significant difference in sensitivity was found among the three methodologies.
CONCLUSIONS: From the results, we can conclude that after careful in-laboratory validation, HRM is a good alternative to the ARMS and Sanger sequencing for KRAS mutation testing.

Taniguchi H, Yamazaki K, Yoshino T, et al.
Japanese Society of Medical Oncology Clinical Guidelines: RAS (KRAS/NRAS) mutation testing in colorectal cancer patients.
Cancer Sci. 2015; 106(3):324-7 [PubMed] Related Publications
The Japanese guidelines for the testing of KRAS mutations in colorectal cancer have been used for the past 5 years. However, new findings of RAS (KRAS/NRAS) mutations that can further predict the therapeutic effects of anti-epidermal growth factor receptor (EGFR) antibody therapy necessitated a revision of the guidelines. The revised guidelines included the following five basic requirements for RAS mutation testing to highlight a patient group in which anti-EGFR antibody therapy may be ineffective: First, anti-EGFR antibody therapy may not offer survival benefit and/or tumor shrinkage to patients with expanded RAS mutations. Thus, current methods to detect KRAS exon 2 (codons 12 and 13) mutations are insufficient for selecting appropriate candidates for this therapy. Additional testing of extended KRAS/NRAS mutations is recommended. Second, repeated tests are not required for the detection; tissue materials of either primary or metastatic lesions are applicable for RAS mutation testing. Evaluating RAS mutations prior to anti-EGFR antibody therapy is recommended. Third, direct sequencing with manual dissection or allele-specific PCR-based methods is currently applicable for RAS mutation testing. Fourth, thinly sliced sections of formalin-fixed, paraffin-embedded tissue blocks are applicable for RAS mutation testing. One section stained with H&E should be provided to histologically determine whether the tissue contains sufficient amount of tumor cells for testing. Finally, RAS mutation testing must be performed in laboratories with appropriate testing procedures and specimen management practices.

Pietrantonio F, Petrelli F, Coinu A, et al.
Predictive role of BRAF mutations in patients with advanced colorectal cancer receiving cetuximab and panitumumab: a meta-analysis.
Eur J Cancer. 2015; 51(5):587-94 [PubMed] Related Publications
BACKGROUND: Wild type RAS (RAS-wt) status is predictive of the activities of the anti-epidermal growth factor receptor (EGFR) monoclonal antibodies cetuximab (C) and panitumumab (P). We examined the impact of C and P on progression-free survival (PFS), overall survival (OS) and overall response rate (ORR) in advanced colorectal cancer (CRC) patients who have RAS-wt/BRAF-mutant (BRAF-mut) status.
METHODS: Randomised trials that compared C or P plus chemotherapy (or C or P monotherapy) with standard therapy or best supportive care (BSC) were included. We used published hazard ratios (HRs) if they were available, or we derived treatment estimates from other survival data. Pooled estimates of the treatment efficacy of anti-EGFR-based therapy with C or P for the RAS-wt/BRAF-mut subgroup were calculated with the random-effect inverse variance weighted method. All statistical tests were two-sided.
RESULTS: Nine phase III trials and one phase II trial (six first-line and two second-line trials, plus two trials involving chemorefractory patients), that included 463 RAS-wt/BRAF-mut CRC patients, were analysed. Overall, the addition of C or P treatment in the BRAF-mut subgroup did not significantly improve PFS (HR, 0.88; 95% confidence interval (CI), 0.67-1.14; p=0.33), OS (HR, 0.91; 95% CI, 0.62-1.34; p=0.63) and ORR (relative risk, 1.31; 95% CI 0.83-2.08, p=0.25) compared with control regimens.
CONCLUSIONS: C- or P-based therapy did not increase the benefit of standard therapy or the BSC in RAS-wt/BRAF-mut CRC patients. These findings support BRAF mutation assessment before initiation of treatment with anti-EGFR monoclonal antibodies.

Mesía R, Henke M, Fortin A, et al.
Chemoradiotherapy with or without panitumumab in patients with unresected, locally advanced squamous-cell carcinoma of the head and neck (CONCERT-1): a randomised, controlled, open-label phase 2 trial.
Lancet Oncol. 2015; 16(2):208-20 [PubMed] Related Publications
BACKGROUND: Panitumumab is a fully human monoclonal antibody that targets EGFR. We aimed to compare chemoradiotherapy plus panitumumab with chemoradiotherapy alone in patients with unresected, locally advanced squamous-cell carcinoma of the head and neck.
METHODS: In this international, open-label, randomised, controlled, phase 2 trial, we recruited patients with locally advanced squamous-cell carcinoma of the head and neck from 41 sites in nine countries worldwide. Patients aged 18 years and older with stage III, IVa, or IVb, previously untreated, measurable (≥ 10 mm for at least one dimension), locally advanced squamous-cell carcinoma of the head and neck (non-nasopharygeal) and an Eastern Cooperative Oncology Group performance status of 0-1 were randomly assigned (2:3) by an independent vendor to open-label chemoradiotherapy (three cycles of cisplatin 100 mg/m(2)) or panitumumab plus chemoradiotherapy (three cycles of intravenous panitumumab 9.0 mg/kg every 3 weeks plus cisplatin 75 mg/m(2)) using stratified randomisation with a block size of five. All patients received 70 Gy to gross tumour and 50 Gy to areas at risk for subclinical disease with standard fractionation. The primary endpoint was local-regional control at 2 years, analysed in all randomised patients who received at least one dose of their assigned protocol-specific treatment (chemotherapy, radiation, or panitumumab). The trial is closed and this is the final analysis. This trial is registered with ClinicalTrials.gov, number NCT00500760.
FINDINGS: Between Oct 26, 2007, and March 26, 2009, 153 patients were enrolled and 150 received treatment (63 in the chemoradiotherapy group and 87 in the panitumumab plus chemoradiotherapy group). Local-regional control at 2 years was 68% (95% CI 54-78) in the chemoradiotherapy group and 61% (50-71) in the panitumumab plus chemoradiotherapy group. The most frequent grade 3-4 adverse events were dysphagia (17 [27%] of 63 patients in the chemoradiotherapy group vs 35 [40%] of 87 in the panitumumab plus chemoradiotherapy group), mucosal inflammation (15 [24%] vs 48 [55%]), and radiation skin injury (eight [13%] vs 27 [31%]). Serious adverse events were reported in 20 (32%) of 63 patients in the chemoradiotherapy group and in 37 (43%) of 87 patients in the panitumumab plus chemoradiotherapy group.
INTERPRETATION: In patients with locally advanced squamous-cell carcinoma of the head and neck, the addition of panitumumab to standard fractionation radiotherapy and cisplatin did not confer any benefit, and the role of EGFR inhibition in these patients needs to be reassessed.
FUNDING: Amgen.

Giralt J, Trigo J, Nuyts S, et al.
Panitumumab plus radiotherapy versus chemoradiotherapy in patients with unresected, locally advanced squamous-cell carcinoma of the head and neck (CONCERT-2): a randomised, controlled, open-label phase 2 trial.
Lancet Oncol. 2015; 16(2):221-32 [PubMed] Related Publications
BACKGROUND: We aimed to compare panitumumab, a fully human monoclonal antibody against EGFR, plus radiotherapy with chemoradiotherapy in patients with unresected, locally advanced squamous-cell carcinoma of the head and neck.
METHODS: In this international, open-label, randomised, controlled, phase 2 trial, we recruited patients with locally advanced squamous-cell carcinoma of the head and neck from 22 sites in eight countries worldwide. Patients aged 18 years and older with stage III, IVa, or IVb, previously untreated, measurable (≥ 10 mm for at least one dimension), locally advanced squamous-cell carcinoma of the head and neck (non-nasopharygeal) and an Eastern Cooperative Oncology Group performance status of 0-1 were randomly assigned (2:3) by an independent vendor to open-label chemoradiotherapy (two cycles of cisplatin 100 mg/m(2) during radiotherapy) or to radiotherapy plus panitumumab (three cycles of panitumumab 9 mg/kg every 3 weeks administered with radiotherapy) using a stratified randomisation with a block size of five. All patients received 70-72 Gy to gross tumour and 54 Gy to areas of subclinical disease with accelerated fractionation radiotherapy. The primary endpoint was local-regional control at 2 years, analysed in all randomly assigned patients who received at least one dose of their assigned protocol-specific treatment (chemotherapy, radiation, or panitumumab). The trial is closed and this is the final analysis. This study is registered with ClinicalTrials.gov, number NCT00547157.
FINDINGS: Between Nov 30, 2007, and Nov 16, 2009, 152 patients were enrolled, and 151 received treatment (61 in the chemoradiotherapy group and 90 in the radiotherapy plus panitumumab group). Local-regional control at 2 years was 61% (95% CI 47-72) in the chemoradiotherapy group and 51% (40-62) in the radiotherapy plus panitumumab group. The most frequent grade 3-4 adverse events were mucosal inflammation (25 [40%] of 62 patients in the chemoradiotherapy group vs 37 [42%] of 89 patients in the radiotherapy plus panitumumab group), dysphagia (20 [32%] vs 36 [40%]), and radiation skin injury (seven [11%] vs 21 [24%]). Serious adverse events were reported in 25 (40%) of 62 patients in the chemoradiotherapy group and in 30 (34%) of 89 patients in the radiotherapy plus panitumumab group.
INTERPRETATION: Panitumumab cannot replace cisplatin in the combined treatment with radiotherapy for unresected stage III-IVb squamous-cell carcinoma of the head and neck, and the role of EGFR inhibition in locally advanced squamous-cell carcinoma of the head and neck needs to be reassessed.
FUNDING: Amgen.

Gill S, Dowden S, Colwell B, et al.
Navigating later lines of treatment for advanced colorectal cancer - optimizing targeted biological therapies to improve outcomes.
Cancer Treat Rev. 2014; 40(10):1171-81 [PubMed] Related Publications
Colorectal cancer (CRC) is the third most commonly diagnosed cancer among males and second among females worldwide. The treatment landscape for advanced CRC (aCRC) is rapidly evolving and there are now a number of randomized trials assessing treatment of aCRC beyond first-line, prompting important questions about how to optimize therapy and maximize benefit. The availability of targeted agents has increased the complexity of post-progression treatment of aCRC. Targeted biological agents with varying modes of action are now approved for use in second-line and beyond, including the VEGF-inhibitors bevacizumab and aflibercept, the VEGFR/multikinase-inhibitor regorafenib, and the EGFR-inhibitors cetuximab and panitumumab. This article provides a systematic overview of the available phase III trial data, discusses biomarkers predictive of response to treatment, addresses safety concerns associated with specific agents, and provides practical, evidence-based recommendations for the later lines of treatment for patients with unresectable aCRC.

Augustine TA, Baig M, Sood A, et al.
Telomere length is a novel predictive biomarker of sensitivity to anti-EGFR therapy in metastatic colorectal cancer.
Br J Cancer. 2015; 112(2):313-8 [PubMed] Article available free on PMC after 20/01/2016 Related Publications
BACKGROUND: Telomeres are TTAGGG tandem repeats capping chromosomal ends and partially controlled by the telomerase enzyme. The EGFR pathway putatively regulates telomerase function, prompting an investigation of telomere length (TL) and its association with anti-epidermal growth factor receptor (EGFR) therapy in metastatic colorectal cancer (mCRC).
METHODS: Colorectal cancer cell lines were treated with multiple drugs and sensitivity determined. Clinical information was gathered from 75 patients who had received anti-EGFR drugs. Telomere length was measured using a validated qRT-PCR technique.
RESULTS: In CRC cell lines, TL independently predicted cetuximab sensitivity. Cells with shorter TL had growth inhibition of 18.6±3.41% as compared with 41.39±8.58% in longer TL (P=0.02). These in vitro findings were validated clinically, in a robust multivariate model. Among patients with KRas WT tumours, those with longer TL had a superior median progression-free survival (PFS) of 24.9 weeks than those with shorter TL; median 11.1 weeks, HR 0.31; P=0.048.
CONCLUSION: Telomere length could be a potential unique biomarker predictive of clinical benefit (PFS) of mCRC patients treated with anti-EGFR therapy. This is the novel demonstration of a complex hitherto undescribed interaction, placing anti-EGFR therapy, EGFR pathway, and the telomerase complex within a clinical context.

Malapelle U, Vigliar E, Sgariglia R, et al.
Ion Torrent next-generation sequencing for routine identification of clinically relevant mutations in colorectal cancer patients.
J Clin Pathol. 2015; 68(1):64-8 [PubMed] Related Publications
AIMS: To evaluate the accuracy, consumable cost and time around testing (TAT) of a next-generation sequencing (NGS) assay, the Ion Torrent AmpliSeq Colon and Lung Cancer Panel, as an alternative to Sanger sequencing to genotype KRAS, NRAS and BRAF in colorectal cancer patients.
METHODS: The Ion Torrent panel was first verified on cell lines and on control samples and then prospectively applied to routine specimens (n=114), with Sanger sequencing as reference.
RESULTS: The Ion Torrent panel detected mutant alleles at the 5% level on cell lines and correctly classified all control tissues. The Ion Torrent assay was successfully carried out on most (95.6%) routine diagnostic samples. Of these, 12 (11%) harboured mutations in the BRAF gene and 47 (43%) in either of the two RAS genes, in two cases with a low abundance of RAS mutant allele which was missed by Sanger sequencing. The mean TAT, from sample receipt to reporting, was 10.4 (Sanger) and 13.0 (Ion Torrent) working days. The consumable cost for genotyping KRAS, NRAS and BRAF was €196 (Sanger) and €187 (Ion Torrent).
CONCLUSIONS: Ion Torrent AmpliSeq Colon and Lung Cancer Panel sequencing is as robust as Sanger sequencing in routine diagnostics to select patients for anti-epidermal growth factor receptor (EGFR) therapy for metastatic colorectal cancer.

Aoyagi K, Kouhuji K, Kizaki J, et al.
Molecular targeting to treat gastric cancer.
World J Gastroenterol. 2014; 20(38):13741-55 [PubMed] Article available free on PMC after 20/01/2016 Related Publications
Trastuzumab that targets human epidermal growth factor receptor 2 (HER2) protein is the only approved molecular targeting agent for treating gastric cancer in Japan and the outcomes have been favorable. However, trastuzumab is effective for only 10% to 20% of the population with gastric cancer that expresses HER2 protein. Molecular targeting therapy with bevacizumab against vascular endothelial growth factors (VEGF) and with cetuximab and panitumumab against the epidermal growth factors pathway that have been approved for treating colorectal cancer are not considered effective for treating gastric cancer according to several clinical trials. However, ramucirumab that targets VEGF receptor-2 prolonged overall survival in a large phase III clinical trial and it might be an effective molecular targeting therapy for gastric cancer. The significance of molecular targeting therapy for gastric cancer remains controversial. A large-scale randomized clinical trial of novel molecular targeting agents with which to treat gastric cancer is needed.

de Boer E, Warram JM, Hartmans E, et al.
A standardized light-emitting diode device for photoimmunotherapy.
J Nucl Med. 2014; 55(11):1893-8 [PubMed] Related Publications
UNLABELLED: Antibody-based photodynamic therapy-photoimmunotherapy (PIT)-is an ideal modality to improve cancer treatment because of its selective and tumor-specific mode of therapy. Because the use of PIT for cancer treatment is continuing to be described, there is great need to characterize a standardized light source for PIT application. In this work, we designed and manufactured a light-emitting diode (LED)/PIT device and validated the technical feasibility, applicability, safety, and consistency of the system for cancer treatment.
METHODS: To outline the characteristics and photobiologic safety of the LED device, multiple optical measurements were performed in accordance with a photobiologic safety standard. A luciferase-transfected breast cancer cell line (2LMP-Luc) in combination with panitumumab-IRDye 700DX (pan-IR700) was used to validate the in vitro and in vivo performance of our LED device.
RESULTS: Testing revealed the light source to be safe, easy to use, and independent of illumination and power output (mW cm(-2)) variations over time. For in vitro studies, an LED dose (2, 4, 6 J cm(-2))-dependent cytotoxicity was observed using propidium iodide exclusion and annexin V staining. Dose-dependent blebbing was also observed during microscopic analysis. Bioluminescence signals of tumors treated with 0.3 mg of pan-IR700 and 50 J cm(-2) decreased significantly (>80%) compared with signals of contralateral nontreated sites at 4 h and at 1 d after PIT.
CONCLUSION: To our knowledge, a normalized and standardized LED device has not been explicitly described or developed. In this article, we introduce a standardized light source and validate its usability for PIT applications.

Misale S, Di Nicolantonio F, Sartore-Bianchi A, et al.
Resistance to anti-EGFR therapy in colorectal cancer: from heterogeneity to convergent evolution.
Cancer Discov. 2014; 4(11):1269-80 [PubMed] Related Publications
UNLABELLED: The EGFR-targeted antibodies cetuximab and panitumumab are used to treat metastatic colorectal cancers. Mutations in KRAS, NRAS, and BRAF and amplification of ERBB2 and MET drive primary (de novo) resistance to anti-EGFR treatment. Recently, the emergence of alterations in the same genes was detected in patients who responded to EGFR blockade and then relapsed. These results illuminate a striking overlap between genes that, when mutated, drive primary and secondary resistance to anti-EGFR antibodies. Remarkably, although the mechanisms of resistance are genetically heterogeneous, they biochemically converge on key signaling pathways. This knowledge is being translated in the rational design of additional lines of therapy.
SIGNIFICANCE: Anti-EGFR-targeted therapies are used for the treatment of metastatic colorectal cancer. Molecular heterogeneity impairs their efficacy by fuelling de novo and acquired resistance. In this review, we highlight how genetically distinct resistance mechanisms biochemically converge on a limited number of signaling pathways that can be therapeutically intercepted.

Gasparini G, Buttitta F, D'Andrea MR, et al.
Optimizing single agent panitumumab therapy in pre-treated advanced colorectal cancer.
Neoplasia. 2014; 16(9):751-6 [PubMed] Article available free on PMC after 20/01/2016 Related Publications
PURPOSE: To improve the selection of advanced colorectal cancer patients to panitumumab by optimizing the assessment of RAS (KRAS-NRAS) mutations.
EXPERIMENTAL DESIGN: Using a centralized pyrosequencing RAS assay, we analyzed the tumors of 94 patients, wild-type for KRAS mutations (codons 12 to 13) by Sanger sequencing (SS), treated with panitumumab.
RESULTS: By SS analysis, 94 (62%) of 152 patients were wild-type and their objective response rate to panitumumab was 17%. We first optimized the KRAS test, by performing an accurate tissue-dissection step followed by pyrosequencing, a more sensitive method, and found further mutations in 12 (12.8%) cases. Secondly, tumors were subjected to RAS extension analysis (KRAS, exons 3 to 4; NRAS exons 2 to 4) by pyrosequencing that allowed to identify several rare mutations: KRAS codon 61, 5.3%; codon 146, 5.3%; NRAS, 9.5%. Overall, RAS mutation rate was 32.9%. All patients with additional RAS mutations had progressive or stable disease, except 3 patients with mutations at codon 61 of KRAS or NRAS who experienced partial (2 cases) or complete response. By excluding from the analysis 11 cases with mutations at codons 61, no patient was responsive to treatment (P=.021). RAS wild-type versus RAS mutated cases had a significantly better time to progression (P=.044), that resulted improved (p=.004) by excluding codon 61 mutations.
CONCLUSION: This study shows that by optimizing the RAS test it is possible to significantly improve the identification of patients who do not gain benefit of panitumumab. Prospective studies are warranted to determine the clinical significance of rare mutations.

Graham CN, Hechmati G, Hjelmgren J, et al.
Cost-effectiveness analysis of panitumumab plus mFOLFOX6 compared with bevacizumab plus mFOLFOX6 for first-line treatment of patients with wild-type RAS metastatic colorectal cancer.
Eur J Cancer. 2014; 50(16):2791-801 [PubMed] Related Publications
OBJECTIVE: To investigate the cost-effectiveness of panitumumab plus mFOLFOX6 (oxaliplatin, 5-fluorouracil and leucovorin) compared with bevacizumab plus mFOLFOX6 in first-line treatment of patients with wild-type RAS metastatic colorectal cancer (mCRC).
DESIGN: A semi-Markov model was constructed from a French health collective perspective, with health states related to first-line treatment (progression-free), disease progression with and without subsequent active treatment, resection of metastases, disease-free after successful resection and death.
METHODS: Parametric survival analyses of patient-level progression-free and overall survival data from the only head-to-head clinical trial of panitumumab and bevacizumab (PEAK) were performed to estimate transitions to disease progression and death. Additional data from PEAK informed the amount of each drug consumed, duration of therapy, subsequent therapy use, and toxicities related to mCRC treatment. Literature and French public data sources were used to estimate unit costs associated with treatment and duration of subsequent active therapies. Utility weights were calculated from patient-level data from panitumumab trials in the first-, second- and third-line settings. A life-time perspective was applied. Scenario, one-way, and probabilistic sensitivity analyses were performed.
RESULTS: Based on a head-to-head clinical trial that demonstrates better efficacy outcomes for patients with wild-type RAS mCRC who receive panitumumab plus mFOLFOX6 versus bevacizumab plus mFOLFOX6, the incremental cost per life-year gained was estimated to be €26,918, and the incremental cost per quality-adjusted life year (QALY) gained was estimated to be €36,577. Sensitivity analyses indicate the model is robust to alternative parameters and assumptions.
CONCLUSIONS: The incremental cost per QALY gained indicates that panitumumab plus mFOLFOX6 represents good value for money in comparison to bevacizumab plus mFOLFOX6 and, with a willingness-to-pay ranging from €40,000 to €60,000, can be considered cost-effective in first-line treatment of patients with wild-type RAS mCRC.

Cheng AL, Li J, Vaid AK, et al.
Adaptation of international guidelines for metastatic colorectal cancer: an asian consensus.
Clin Colorectal Cancer. 2014; 13(3):145-55 [PubMed] Related Publications
Colorectal cancer (CRC) is among the most common cancers worldwide, but marked epidemiological differences exist between Asian and non-Asian populations. Hence, a consensus meeting was held in Hong Kong in December 2012 to develop Asia-specific guidelines for the management of metastatic CRC (mCRC). A multidisciplinary expert panel, consisting of 23 participants from 10 Asian and 2 European countries, discussed current guidelines for colon or rectal cancer and developed recommendations for adapting these guidelines to Asian clinical practice. Participants agreed that mCRC management in Asia largely follows international guidelines, but they proposed a number of recommendations based on regional 'real-world' experience. In general, participants agreed that 5-fluorouracil (5-FU) infusion regimens in doublets can be substituted with UFT (capecitabine, tegafur-uracil) and S1 (tegafur, 5-chloro-2,4-dihydroxypyridine and oxonic acid), and that the monoclonal antibodies cetuximab and panitumumab are recommended for KRAS wild type tumors. For KRAS mutant tumors, bevacizumab is the preferred biological therapy. FOLFOX (folinic acid, 5-FU, and oxaliplatin) is preferred for initial therapy in Asian patients. The management of mCRC is evolving, and it must be emphasized that the recommendations presented here reflect current treatment practices and thus might change as more data become available.

Stiegelbauer V, Perakis S, Deutsch A, et al.
MicroRNAs as novel predictive biomarkers and therapeutic targets in colorectal cancer.
World J Gastroenterol. 2014; 20(33):11727-35 [PubMed] Article available free on PMC after 20/01/2016 Related Publications
Colorectal cancer (CRC) is the third most common cancer in western countries. Despite significant improvement in available treatment options, CRC still remains the second leading cause of cancer-related death. Traditionally, 5-fluorouracil has been used as the main chemotherapy drug for treatment of metastatic CRC (mCRC). However, during the last two decades more effective chemotherapeutic agents such as oxaliplatin, irinotecan and the monoclonal antibodies cetuximab, panitumumab and bevacizumab have been used in clinical practice. More recently, the therapeutic armamentarium has been supplemented by the monoclonal antibodies bevacizumab, cetuximab and panitumumab as well as the protein-trap aflibercept and the small molecule multi-kinase inhibitor regorafenib. One of the major problems for the management of CRC is the inherent or acquired resistance to therapeutic approaches. The discovery of microRNAs (miRNAs), a class of small, endogenous, non-coding, single-stranded RNAs that play a role as post-transcriptional regulators, has added new dimensions to the diagnosis and treatment of cancer. Because miRNAs are important regulators of carcinogenesis, progression, invasion, angiogenesis and metastases in CRC, they might serve as potential predictive and prognostic factors and even as therapeutic targets themselves. Several miRNAs are already known to be dysregulated in CRCs and have been linked to biological processes involved in tumor progression and response to anti-cancer therapies. This review summarizes current therapeutic approaches for treating CRC and highlights the role of miRNAs as novel predictive biomarkers and potential drug targets in CRC patients.

Kordes S, van Berge Henegouwen MI, Hulshof MC, et al.
Preoperative chemoradiation therapy in combination with panitumumab for patients with resectable esophageal cancer: the PACT study.
Int J Radiat Oncol Biol Phys. 2014; 90(1):190-6 [PubMed] Related Publications
PURPOSE: Preoperative chemoradiation therapy (CRT) has become the standard treatment strategy for patients with resectable esophageal cancer. This multicenter phase 2 study investigated the efficacy of the addition of the epidermal growth factor receptor (EGFR) inhibitor panitumumab to a preoperative CRT regimen with carboplatin, paclitaxel, and radiation therapy in patients with resectable esophageal cancer.
METHODS AND MATERIALS: Patients with resectable cT1N1M0 or cT2-3N0 to -2M0 tumors received preoperative CRT consisting of panitumumab (6 mg/kg) on days 1, 15, and 29, weekly administrations of carboplatin (area under the curve [AUC] = 2), and paclitaxel (50 mg/m(2)) for 5 weeks and concurrent radiation therapy (41.4 Gy in 23 fractions, 5 days per week), followed by surgery. Primary endpoint was pathologic complete response (pCR) rate. We aimed at a pCR rate of more than 40%. Furthermore, we explored the predictive value of biomarkers (EGFR, HER 2, and P53) for pCR.
RESULTS: From January 2010 until December 2011, 90 patients were enrolled. Patients were diagnosed predominantly with adenocarcinoma (AC) (80%), T3 disease (89%), and were node positive (81%). Three patients were not resected due to progressive disease. The primary aim was unmet, with a pCR rate of 22%. Patients with AC and squamous cell carcinoma reached a pCR of 14% and 47%, respectively. R0 resection was achieved in 95% of the patients. Main grade 3 toxicities were rash (12%), fatigue (11%), and nonfebrile neutropenia (11%). None of the biomarkers was predictive for response.
CONCLUSIONS: The addition of panitumumab to CRT with carboplatin and paclitaxel was safe and well tolerated but could not improve pCR rate to the preset criterion of 40%.

Boeckx C, Op de Beeck K, Wouters A, et al.
Overcoming cetuximab resistance in HNSCC: the role of AURKB and DUSP proteins.
Cancer Lett. 2014; 354(2):365-77 [PubMed] Related Publications
Unraveling the underlying mechanisms of cetuximab resistance in head and neck squamous cell carcinoma (HNSCC) is of major importance as many tumors remain non-responsive or become resistant. Our microarray results suggest that "resistant" cells still exhibit RAS-MAPK pathway signaling contributing to drug resistance, as witnessed by low expression of DUSP5 and DUSP6, negative regulators of ERK1/2, and increased expression of AURKB, a key regulator of mitosis. Therefore, interrupting the RAS-MAPK pathway by an ERK1/2 inhibitor (apigenin) or an AURKB inhibitor (barasertib) might be a new strategy for overcoming cetuximab resistance in HNSCC.

Saridaki Z, Weidhaas JB, Lenz HJ, et al.
A let-7 microRNA-binding site polymorphism in KRAS predicts improved outcome in patients with metastatic colorectal cancer treated with salvage cetuximab/panitumumab monotherapy.
Clin Cancer Res. 2014; 20(17):4499-510 [PubMed] Article available free on PMC after 01/09/2015 Related Publications
PURPOSE: An inherited mutation in KRAS (LCS6-variant or rs61764370) results in altered control of the KRAS oncogene. We studied this biomarker's correlation to anti-EGFR monoclonal antibody (mAb) therapy response in patients with metastatic colorectal cancer.
EXPERIMENTAL DESIGN: LCS6-variant and KRAS/BRAF mutational status was determined in 512 patients with metastatic colorectal cancer treated with salvage anti-EGFR mAb therapy, and findings correlated with outcome. Reporters were tested in colon cancer cell lines to evaluate the differential response of the LCS6-variant allele to therapy exposure.
RESULTS: In this study, 21.2% (109 of 512) of patients with metastatic colorectal cancer had the LCS6-variant (TG/GG), which was found twice as frequently in the BRAF-mutated versus the wild-type (WT) group (P=0.03). LCS6-variant patients had significantly longer progression-free survival (PFS) with anti-EGFR mAb monotherapy treatment in the whole cohort (16.85 vs. 7.85 weeks; P=0.019) and in the double WT (KRAS and BRAF) patient population (18 vs. 10.4 weeks; P=0.039). Combination therapy (mAbs plus chemotherapy) led to improved PFS and overall survival (OS) for nonvariant patients, and brought their outcome to levels comparable with LCS6-variant patients receiving anti-EGFR mAb monotherapy. Combination therapy did not lead to improved PFS or OS for LCS6-variant patients. Cell line studies confirmed a unique response of the LCS6-variant allele to both anti-EGFR mAb monotherapy and chemotherapy.
CONCLUSIONS: LCS6-variant patients with metastatic colorectal cancer have an excellent response to anti-EGFR mAb monotherapy, without any benefit from the addition of chemotherapy. These findings further confirm the importance of this mutation as a biomarker of anti-EGFR mAb response in patients with metastatic colorectal cancer, and warrant further prospective confirmation.

Kalikaki A, Politaki H, Souglakos J, et al.
KRAS genotypic changes of circulating tumor cells during treatment of patients with metastatic colorectal cancer.
PLoS One. 2014; 9(8):e104902 [PubMed] Article available free on PMC after 01/09/2015 Related Publications
INTRODUCTION: Circulating tumor cells (CTCs) could represent a non-invasive source of cancer cells used for longitudinal monitoring of the tumoral mutation status throughout the course of the disease. The aims of the present study were to investigate the detection of KRAS mutations in CTCs from patients with metastatic colorectal cancer (mCRC) and to compare their mutation status during treatment or disease progression with that of the corresponding primary tumors.
MATERIALS AND METHODS: Identification of the seven most common KRAS mutations on codons 12 and 13 was performed by Peptide Nucleic Acid (PNA)-based qPCR method. The sensitivity of the assay was determined after isolation of KRAS mutant cancer cells spiked into healthy donors' blood, using the CellSearch Epithelial Cell kit. Consistent detection of KRAS mutations was achieved in samples containing at least 10 tumor cells/7.5 ml of blood.
RESULTS: The clinical utility of the assay was assessed in 48 blood samples drawn from 31 patients with mCRC. All patients had PIK3CA and BRAF wild type primary tumors and 14 KRAS mutant tumors. CTCs were detected in 65% of specimens obtained from 74% of patients. KRAS mutation analysis in CTC-enriched specimens showed that 45% and 16.7% of patients with mutant and wild type primary tumors, respectively, had detectable mutations in their CTCs. Assessing KRAS mutations in serial blood samples revealed that individual patient's CTCs exhibited different mutational status of KRAS during treatment.
CONCLUSIONS: The current findings support the rationale for using the CTCs as a dynamic source of tumor cells which, by re-evaluating their KRAS mutation status, could predict, perhaps more accurately, the response of mCRC patients to targeted therapy.

Lindberg JM, Newhook TE, Adair SJ, et al.
Co-treatment with panitumumab and trastuzumab augments response to the MEK inhibitor trametinib in a patient-derived xenograft model of pancreatic cancer.
Neoplasia. 2014; 16(7):562-71 [PubMed] Article available free on PMC after 01/09/2015 Related Publications
Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations and epidermal growth factor receptor (EGFR) family signaling are drivers of tumorigenesis in pancreatic ductal adenocarcinoma (PDAC). Previous studies have demonstrated that combinatorial treatment of PDAC xenografts with the mitogen-activated protein kinase-extracellular-signal-regulated kinase (ERK) kinase1/2 (MEK1/2) inhibitor trametinib and the dual EGFR/human epidermal growth factor receptor 2 (HER2) inhibitor lapatinib provided more effective inhibition than either treatment alone. In this study, we have used the therapeutic antibodies, panitumumab (specific for EGFR) and trastuzumab (specific for HER2), to probe the role of EGFR and HER2 signaling in the proliferation of patient-derived xenograft (PDX) tumors. We show that dual anti-EGFR and anti-HER2 therapy significantly augmented the growth inhibitory effects of the MEK1/2 inhibitor trametinib in three different PDX tumors. While significant growth inhibition was observed in both KRAS mutant xenograft groups receiving trametinib and dual antibody therapy (tumors 366 and 608), tumor regression was observed in the KRAS wild-type xenografts (tumor 738) treated in the same manner. Dual antibody therapy in conjunction with trametinib was equally or more effective at inhibiting tumor growth and with lower apparent toxicity than trametinib plus lapatinib. Together, these studies provide further support for a role for EGFR and HER2 in pancreatic cancer proliferation and underscore the importance of therapeutic intervention in both the KRAS-rapidly accelerated fibrosarcoma kinase (RAF)-MEK-ERK and EGFR-HER2 pathways to achieve maximal therapeutic efficacy in patients.

Jeong WJ, Cha PH, Choi KY
Strategies to overcome resistance to epidermal growth factor receptor monoclonal antibody therapy in metastatic colorectal cancer.
World J Gastroenterol. 2014; 20(29):9862-71 [PubMed] Article available free on PMC after 01/09/2015 Related Publications
Administration of monoclonal antibodies (mAbs) against epidermal growth factor receptor (EGFR) such as cetuximab and panitumumab in combination with conventional chemotherapy substantially prolongs survival of patients with metastatic colorectal cancer (mCRC). However, the efficacy of these mAbs is limited due to genetic variation among patients, in particular K-ras mutations. The discovery of K-ras mutation as a predictor of non-responsiveness to EGFR mAb therapy has caused a major change in the treatment of mCRC. Drugs that inhibit transformation caused by oncogenic alterations of Ras and its downstream components such as BRAF, MEK and AKT seem to be promising cancer therapeutics as single agents or when given with EGFR inhibitors. Although multiple therapeutic strategies to overcome EGFR mAb-resistance are under investigation, our understanding of their mode of action is limited. Rational drug development based on stringent preclinical data, biomarker validation, and proper selection of patients is of paramount importance in the treatment of mCRC. In this review, we will discuss diverse approaches to overcome the problem of resistance to existing anti-EGFR therapies and potential future directions for cancer therapies related to the mutational status of genes associated with EGFR-Ras-ERK and PI3K signalings.

De Stefano A, Carlomagno C
Beyond KRAS: Predictive factors of the efficacy of anti-EGFR monoclonal antibodies in the treatment of metastatic colorectal cancer.
World J Gastroenterol. 2014; 20(29):9732-43 [PubMed] Article available free on PMC after 01/09/2015 Related Publications
Systematic analysis of the epidermal growth factor receptor (EGFR) pathway revealed that biomarkers could be used to predict the response to and outcome of anti-EGFR therapies in patients affected by metastatic colorectal cancer. We have conducted a review on the most recent findings and advances on this topic. To this aim, we searched the PubMed database for articles devoted to predictive and prognostic biomarkers for patients administered cetuximab- and panitumumab-based therapies. Here we review the state of the art and the controversies about the molecular factors known to be predictors of the efficacy of anti-EGFR therapy, namely, KRAS, BRAF, NRAS, PI3KCA and PTEN, and we discuss their prognostic value in colorectal cancer patients.

Foote MC, McGrath M, Guminski A, et al.
Phase II study of single-agent panitumumab in patients with incurable cutaneous squamous cell carcinoma.
Ann Oncol. 2014; 25(10):2047-52 [PubMed] Related Publications
BACKGROUND: Although advanced cutaneous squamous cell carcinoma (CSCC) is quite common, there are few prospective trials regarding its optimal management. This study evaluated the efficacy and safety of single-agent panitumumab in the treatment of patients with CSCC not suitable for local therapy.
PATIENTS AND METHODS: Sixteen patients received single-agent panitumumab at a dose of 6 mg/kg repeated every 2 weeks for a minimum of three cycles and continued until progression, a maximum of nine cycles or dose-limiting toxicity. The primary end point was the best overall response rate (ORR) as assessed by Response Evaluation Criteria in Solid Tumours (RECIST version 1.1) criteria. Secondary end points included evaluation of safety, toxicity and progression-free survival (PFS).
RESULTS: Between May 2010 and May 2012, 16 patients were recruited. Fourteen patients were male and the median age was 68 years. Fifteen patients had locoregionally advanced or recurrent disease with 14 patients receiving previous radiotherapy and 7 receiving previous cytotoxic chemotherapy. The best ORR [partial (PR) or complete response (CR)] was 31% (3/16 PR, 2/16 CR) with a further 6 of 16 patients achieving SD. The median PFS and overall survival were 8 and 11 months respectively. Grade 3 or 4 events were observed in five patients (four being skin toxicity) with one patient ceasing due to skin toxicity. With a median follow-up of 24 months, 10 patients died due to progressive disease, 6 are alive, one patient with no evidence of disease at the time of analysis.
CONCLUSIONS: Single-agent panitumumab is safe and effective in the management of patients with advanced CSCC even in a previously extensively pre-treated cohort.

Bergman H, Walton T, Del Bel R, et al.
Managing skin toxicities related to panitumumab.
J Am Acad Dermatol. 2014; 71(4):754-9 [PubMed] Related Publications
BACKGROUND: Dermatologic toxicities from targeted agents such as panitumumab can interfere with cancer treatment.
OBJECTIVE: We sought to evaluate the rash assessment and management in a consecutive patient cohort who received panitumumab for colorectal cancer treatment.
METHODS: This was a retrospective chart review.
RESULTS: Skin toxicity, consisting of papulopustular rash, was experienced by 32 of 34 patients. The majority (85%) developed the rash by the end of the second infusion cycle. Patients presented with a mild (41%), moderate (38%), and severe (21%) rash, and progressed to an extensive rash without appropriate treatment. A grading system was used for 65% of patients to document severity.
LIMITATIONS: Small sample size limited power in analysis. Rash severity had to be inferred based on rash description and management in 11 of the patients.
CONCLUSION: Dermatologic toxicities related to panitumumab are common; however, the way they are reported and managed varies among physicians. To prevent progression, toxicities must be assessed and treated early and aggressively, according to severity grading. Dermatologists could aid oncologists in choosing the best management strategies.

Andrea C, Fausto P, Francesca BK, et al.
Which strategy after first-line therapy in advanced colorectal cancer?
World J Gastroenterol. 2014; 20(27):8921-7 [PubMed] Article available free on PMC after 01/09/2015 Related Publications
Second-line therapy for advanced colorectal cancer is an integral part of the treatment strategy that needs to be set from the beginning for each patient, bearing in mind the expected toxicities of chosen treatments, the patient's clinical condition, comorbidities, preferences, the aims of the treatment and the molecular status. Furthermore, the distinction between lines of therapy is no longer absolute. The perspective of "continuum of care" includes switching chemotherapy prior to disease progression, maintenance therapy, drug "holidays" if needed, surgical resection of metastases in selected patients, and seems to allow a tailored treatment, in which patients are more likely to benefit from exposure to all active agents, which is known to correlate with overall survival. The scenario of second-line treatment has changed dramatically over the years and could currently benefit from several options including chemotherapy with a single agent or in combination and the addition of molecular-targeted agents developed in the last decade, such as epidermal growth factor receptor antibodies (cetuximab, panitumumab) and vascular endothelial growth factor-targeting agents (bevacizumab, aflibercept), with the possibility of bevacizumab use even beyond first progression. The purpose of this review is to summarize the most important scientific data supporting the use of chemotherapy and the new biologic agents in the second-line setting in advanced colorectal cancer.

Dotan E, Devarajan K, D'Silva AJ, et al.
Patterns of use and tolerance of anti-epidermal growth factor receptor antibodies in older adults with metastatic colorectal cancer.
Clin Colorectal Cancer. 2014; 13(3):192-8 [PubMed] Article available free on PMC after 01/09/2015 Related Publications
BACKGROUND: Limited data are available regarding the tolerance of anti-epidermal growth factor receptor (EGFR) antibodies among elderly patients with metastatic colorectal cancer (mCRC). We retrospectively reviewed our experience of treating elderly patients with mCRC with these agents between 2004 and 2011.
METHODS: Patients with mCRC ≥ 65 years treated with anti-EGFR agents were included in this analysis. We recorded demographic and disease characteristics, treatment regimen and duration, KRAS status, and overall survival (OS). Toxicity evaluation included common hematologic and nonhematologic toxicities seen with these agents.
RESULTS: One hundred seventeen patients were included, with a median age at treatment initiation of 73 years (range, 65-86 years), 59% of male sex, 82% with colon primary tumors, and 51% with metastatic disease at presentation. Median time on anti-EGFR treatment was 2.4 months. Older age at treatment initiation was associated with use of anti-EGFR antibody as monotherapy versus combination therapy (P = .0009). Worse performance status (PS) at treatment initiation was associated with a shorter overall survival (OS) (P = .013) and shorter treatment duration (P = .01). The incidence of hematologic/nonhematologic grade ≥ 3 was 36% and 15%, respectively. No association was found between age and presence of grade ≥ 3 toxicity. Longer treatment duration and better PS at treatment initiation were the only factors associated with higher incidence of grade 3 toxicity.
CONCLUSION: Our data demonstrate that anti-EGFR antibodies can be used in older patients with mCRC, with toxicity profiles similar to those reported in large phase III studies of younger patients. Advanced age was associated with receipt of anti-EGFR agents as monotherapy but did not impact treatment outcomes in this population.

Morris V, Overman MJ, Jiang ZQ, et al.
Progression-free survival remains poor over sequential lines of systemic therapy in patients with BRAF-mutated colorectal cancer.
Clin Colorectal Cancer. 2014; 13(3):164-71 [PubMed] Article available free on PMC after 01/09/2015 Related Publications
BACKGROUND: BRAF mutations occur in 5% to 10% of metastatic colorectal cancers and are biomarkers associated with a poor prognosis. However, the outcomes with standard chemotherapy over sequential lines of therapy in a large cohort of patients with BRAF-mutant tumors have not been described.
PATIENTS AND METHODS: We searched the M.D. Anderson Cancer Center databases for patients with colorectal cancer and identified BRAF mutations between December 2003 and May 2012. Patients were analyzed for clinical characteristics, PFS, overall survival, and chemotherapeutic agents used. Survival was estimated according to the Kaplan-Meier method.
RESULTS: Among the 1567 patients tested for BRAF mutations at our institution, 127 (8.1%) had tumors with BRAF mutations. The 71 patients who presented with metastatic disease received a median of 2 lines of chemotherapy. For the first 3 lines of chemotherapy, median PFS was 6.3 months (n = 69 patients; 95% confidence interval [CI], 4.9-7.7 months), 2.5 months (n = 58 patients; 95% CI, 1.8-3.0 months), and 2.6 months (n = 31 patients; 95% CI, 1.0-4.2 months), respectively. Median PFS was not affected by the backbone chemotherapeutic agent in the first-line setting, whether oxaliplatin-based or irinotecan-based (6.4 months vs. 5.4 months, respectively; P = .99).
CONCLUSION: PFS is expectedly poor for patients with BRAF-mutated metastatic colorectal cancer. Despite the ascertainment bias present (with testing preferentially performed in patients suitable for clinical trials in refractory disease), these data provide historic controls suitable for future study design and support the idea that novel therapeutic options are essential in this population.

Landsman-Blumberg PB, Carter GC, Johnson BH, et al.
Metastatic colorectal cancer treatment patterns according to kirsten rat sarcoma viral oncogene homolog genotype in U.S. Community-based oncology practices.
Clin Colorectal Cancer. 2014; 13(3):178-84 [PubMed] Related Publications
INTRODUCTION: In 2008, the National Comprehensive Cancer Network guidelines were revised in light of the identification of the Kirsten Rat Sarcoma Viral Oncogene Homolog (KRAS) gene as a biomarker of nonresponse to epidermal growth factor receptor inhibitors. This study sought to describe and compare real-world treatment patterns of metastatic colorectal cancer (mCRC) according to KRAS genotype in community-based oncology practices in the United States.
MATERIALS AND METHODS: Data from the ACORN (ACORN LLC, Memphis, TN) electronic medical record data warehouse, containing data of approximately 180,000 patients from 12 oncology practices across the United States were used. Records of adult patients with mCRC who had undergone KRAS testing between January 2008 and December 2011 were evaluated. Patient demographic characteristics, KRAS genotype, and treatment patterns were identified and compared.
RESULTS: Six hundred forty-eight mCRC patients who were tested for KRAS were identified. Of these, 48.1% had wild type (WT), 42.3% mutant, and 9.6% unknown genotypes. Most patients (72.1%) were tested in 2009 or later, after the guideline revision. Bevacizumab-containing combinations were the most common first-line regimens in KRAS mutant and WT patients. Approximately 90% of patients received at least 1 line of therapy, however, WT patients received significantly more lines of therapy than KRAS mutant patients (2.6 ± 1.5 vs. 2.1 ± 1.2; P < .001).
CONCLUSIONS: KRAS WT and mutant genotypes had similar first-line regimens; however, WT patients received more lines of therapy. Although there does not appear to be a lag between changes in guidelines and treatment practice, professional and government organizations must keep up with the changing science and disseminate this information to oncologists in a timely manner.

Psyrri A, Rampias T, Vermorken JB
The current and future impact of human papillomavirus on treatment of squamous cell carcinoma of the head and neck.
Ann Oncol. 2014; 25(11):2101-15 [PubMed] Related Publications
BACKGROUND: Squamous cell carcinoma of the head and neck (SCCHN) was traditionally associated with smoking and alcohol use; however, human papillomavirus (HPV) infection has recently been implicated as a novel risk factor for oropharyngeal tumors. Furthermore, HPV-associated oropharyngeal carcinoma (OPC) appears to be a distinct entity with different epidemiology, biology, and clinical outcomes.
METHODS: Here, we comprehensively review the existing data regarding HPV status and prognostic or predictive outcomes in both the locoregionally advanced (LA) and recurrent/metastatic (RM) disease setting and discuss ongoing trials that may eventually impact the treatment of patients with HPV-positive (HPV+) SCCHN.
RESULTS: A body of retrospective and prospective data established an association between HPV+ OPC and better survival, particularly for LA disease. Current data on RM disease are limited, but they also suggest prognostic significance for HPV.
CONCLUSIONS: Better outcomes in HPV+ LA disease may allow for less aggressive treatment in the future, and several trials are evaluating deintensified regimens in patients with HPV+, LA OPC; it should be emphasized that deintensification strategies are appropriate only in a clinical research setting and only for selected subgroups of HPV+ patients. In addition, HPV-targeted strategies, such as vaccines, are currently undergoing clinical evaluation. On the other hand, the prognostic impact of HPV in RM disease requires further validation before any modifications in treatment can be made. Likewise, the predictive significance of HPV status in both disease settings remains to be defined.
CLINICAL TRIAL NUMBERS: NCT00226239, NCT00301028, NCT00387127, NCT00410826, NCT00503997, NCT00514943, NCT00544414, NCT00768664, NCT00939627, NCT01084083, NCT01302834, NCT01687413, NCT01706939.

Tang NP, Li H, Qiu YL, et al.
Risk/benefit profile of panitumumab-based therapy in patients with metastatic colorectal cancer: evidence from five randomized controlled trials.
Tumour Biol. 2014; 35(10):10409-18 [PubMed] Related Publications
This study aims to evaluate the risk and benefit profiles of panitumumab-based therapy (PBT) in patients with metastatic colorectal cancer (mCRC). Relevant randomized controlled trials were identified by searching PubMed, Medline, EMBASE and Cochrane Library. Data on progression-free survival (PFS), overall survival (OS), all grade and severe (grade ≥3) adverse events were extracted and pooled to calculate hazard ratios (HRs) and risk ratios (RRs) with 95 % confidence intervals (CIs). Number needed to treat (NNT) for PFS and number needed to harm (NNH) for significantly changed toxicities were calculated. A total of 4,155 patients were included in the analysis. PBT significantly improved PFS (HRrandom = 0.66, 95 % CI = 0.45-0.95) but not OS (HRfixed = 0.93, 95 % CI = 0.83-1.04) when used in the subsequent-line setting. The effect on PFS was more evident in patients with wild-type KRAS (HRrandom = 0.64, 95 % CI = 0.47-0.87) and the NNT for PFS is 11 to 23at 1 year. PBT did not benefit patients when used in the first-line setting. In addition, PBT significantly increased the risk of skin toxicity, infections, diarrhea, dehydration, mucositis, hypokalemia, fatigue, hypomagnesemia, pulmonary embolism and paronychia. The NNHs for skin toxicity, diarrhea, infection, hypokalemia and mucositis are less than 23. In conclusion, when used in the subsequent-line setting, PBT can improve the disease progression, especially in mCRC patients with wild-type KRAS. Regarding the adverse events associated with the PBT, close monitoring and necessary preparations are recommended during the therapy.

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