BACKGROUND: Anti-epidermal growth factor receptor monoclonal antibodies (panitumumab [P] and cetuximab [C]) are approved and effective only in KRAS wild-type patients with advanced colorectal cancer. The purpose of our meta-analysis is to evaluate the real effects of C and P in KRAS wild-type patients treated in randomized trials. PATIENTS AND METHODS: Eligible studies included prospective, randomized, and controlled trials in which either C or P had been added to standard antineoplastic therapy or best supportive care and data for KRAS wild-type patients only had been calculated. Six thousand three hundred ninety-five patients' tumor samples have been analyzed (total wild-type n = 3,254; experimental arm n = 1,608; control arm n = 1,646). Relative risks (RRs) with 95% confidence intervals (CIs) for response rate were calculated, as well as hazard ratios (HRs)for progression-free survival (PFS) and overall survival. RESULTS: The overall RR of response rate is 1.69 (p = 0.003) in all trials. The overall HRs for PFS and survival are 0.65 (p = 0.0006) and 0.84 (p = 0.03), respectively, and both are significant. The HRs for PFS and survival in C trials are 0.64 and 0.79, respectively, and 0.65 and 0.87, respectively, in P trials, although only the results achieved in P trials are significant (p = 0.0007 and p = 0.03). Both response rate (RR = 10.94) and PFS (HR = 0.51) have increased more in pretreated patients than in first-line trials. CONCLUSION: The addition of anti-EGFR monoclonal antibodies to standard anticancer therapy in KRAS wild-type colorectal cancer showed an overall significantly increased risk of objective response rate and increased progression-free and overall survival. Only the results achieved in P randomized trials are significant, and the strongest results have been achieved in pretreated patients.

RECORD STATUS: None CITATION: National Horizon Scanning Centre. Panitumumab for advanced colorectal cancer - horizon scanning review. Birmingham: National Horizon Scanning Centre (NHSC) 2005: 6

BACKGROUND: Patients with metastatic colorectal cancer that harbors KRAS mutations in exon 2 do not benefit from anti-epidermal growth factor receptor (EGFR) therapy. Other activating RAS mutations may also be negative predictive biomarkers for anti-EGFR therapy. METHODS: In this prospective-retrospective analysis, we assessed the efficacy and safety of panitumumab plus oxaliplatin, fluorouracil, and leucovorin (FOLFOX4) as compared with FOLFOX4 alone, according to RAS (KRAS or NRAS) or BRAF mutation status. A total of 639 patients who had metastatic colorectal cancer without KRAS mutations in exon 2 had results for at least one of the following: KRAS exon 3 or 4; NRAS exon 2, 3, or 4; or BRAF exon 15. The overall rate of ascertainment of RAS status was 90%. RESULTS: Among 512 patients without RAS mutations, progression-free survival was 10.1 months with panitumumab-FOLFOX4 versus 7.9 months with FOLFOX4 alone (hazard ratio for progression or death with combination therapy, 0.72; 95% confidence interval [CI], 0.58 to 0.90; P=0.004). Overall survival was 26.0 months in the panitumumab-FOLFOX4 group versus 20.2 months in the FOLFOX4-alone group (hazard ratio for death, 0.78; 95% CI, 0.62 to 0.99; P=0.04). A total of 108 patients (17%) with nonmutated KRAS exon 2 had other RAS mutations. These mutations were associated with inferior progression-free survival and overall survival with panitumumab-FOLFOX4 treatment, which was consistent with the findings in patients with KRAS mutations in exon 2. BRAF mutations were a negative prognostic factor. No new safety signals were identified. CONCLUSIONS: Additional RAS mutations predicted a lack of response in patients who received panitumumab-FOLFOX4. In patients who had metastatic colorectal cancer without RAS mutations, improvements in overall survival were observed with panitumumab-FOLFOX4 therapy. (Funded by Amgen and others; PRIME ClinicalTrials.gov number, NCT00364013.).

RECORD STATUS: None CITATION: National Horizon Scanning Centre. Panitumumab (Vectibix) for first-line metastatic colorectal cancer Birmingham: National Horizon Scanning Centre (NHSC). Horizon Scanning Technology Briefing. 2008

BACKGROUND: Panitumumab, formerly known as ABX-EGF, was the first recombinant human immunoglobulin G2 monoclonal antibody approved by the US Food and Drug Administration for the treatment of patients with epidermal growth factor receptor-expressing metastatic colorectal cancer (mCRC) refractory to fluoropyrimidine-, oxaliplatin-, and/or irinotecan-containing chemotherapeutic regimens. OBJECTIVE: The purpose of this review was to evaluate the pharmacokinetic and pharmacodynamic properties, clinical efficacy, and safety profile of panitumumab in the treatment of metastatic colorectal cancer. METHODS: Computerized searches of MEDLINE and International Pharmaceutical Abstracts from 1985 to August 15, 2007, were performed with the search terms panitumumab, ABX-EGF, EGFr, and colorectal cancer. All available clinical trials and ongoing trials were included in this review. Relevant abstracts presented at the annual meetings of the American Society of Clinical Oncology, American Association for Cancer Research, and Gastrointestinal Cancer Symposium (1999-2007) also were reviewed and included. RESULTS: Preclinical and clinical studies have established a role for panitumumab in mCRC refractory to multiple chemotherapeutic regimens. In a Phase III trial of panitumumab plus best supportive care (BSC) versus BSC alone in patients with refractory mCRC, panitumumab was found to have efficacy in time-related end points, such as progression-free survival. In the panitumumab group, a significant (46%) reduction in tumor progression rate was reported compared with BSC (hazard ratio, 0.54; 95% CI, 0.44-0.66; P < 0.001). At the present time, the use of panitumumab as first-line treatment for mCRC with standard chemotherapy and bevacizumab is not indicated due to increased toxicity with no advantage in efficacy. The efficacy of panitumumab is being evaluated in other solid tumors, such as lung, breast, ovarian, bladder, and head and neck cancers. CONCLUSION: Panitumumab appears to have relatively acceptable tolerability and is now available as an additional option for patients with mCRC refractory to multiple chemotherapeutic regimens.

RECORD STATUS: None CITATION: Hintringer K. Panitumumab (Vectibix) for the first-line treatment of metastatic colorectal cancer Vienna: Ludwig Boltzmann Institut fuer Health Technology Assessment (LBI-HTA). Decision Support Document: Horizon Scanning in Oncology No.11. 2010

CITATION: National Horizon Scanning Centre. Panitumumab (Vectibix) metastatic and/or recurrent head and neck cancer - first line Birmingham: National Horizon Scanning Centre (NHSC). Horizon Scanning Technology Briefing. 2010

Abstract 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.

PURPOSE: Panitumumab, a fully human antibody against the epidermal growth factor receptor (EGFR), has activity in a subset of patients with metastatic colorectal cancer (mCRC). Although activating mutations in KRAS, a small G-protein downstream of EGFR, correlate with poor response to anti-EGFR antibodies in mCRC, their role as a selection marker has not been established in randomized trials. PATIENTS AND METHODS: KRAS mutations were detected using polymerase chain reaction on DNA from tumor sections collected in a phase III mCRC trial comparing panitumumab monotherapy to best supportive care (BSC). We tested whether the effect of panitumumab on progression-free survival (PFS) differed by KRAS status. RESULTS: KRAS status was ascertained in 427 (92%) of 463 patients (208 panitumumab, 219 BSC). KRAS mutations were found in 43% of patients. The treatment effect on PFS in the wild-type (WT) KRAS group (hazard ratio [HR], 0.45; 95% CI: 0.34 to 0.59) was significantly greater (P < .0001) than in the mutant group (HR, 0.99; 95% CI, 0.73 to 1.36). Median PFS in the WT KRAS group was 12.3 weeks for panitumumab and 7.3 weeks for BSC. Response rates to panitumumab were 17% and 0%, for the WT and mutant groups, respectively. WT KRAS patients had longer overall survival (HR, 0.67; 95% CI, 0.55 to 0.82; treatment arms combined). Consistent with longer exposure, more grade III treatment-related toxicities occurred in the WT KRAS group. No significant differences in toxicity were observed between the WT KRAS group and the overall population. CONCLUSION: Panitumumab monotherapy efficacy in mCRC is confined to patients with WT KRAS tumors. KRAS status should be considered in selecting patients with mCRC as candidates for panitumumab monotherapy.

PURPOSE Cetuximab or panitumumab are effective in 10% to 20% unselected metastatic colorectal cancer (CRC) patients. KRAS mutations account for approximately 30% to 40% patients who are not responsive. The serine-threonine kinase BRAF is the principal effector of KRAS. We hypothesized that, in KRAS wild-type patients, BRAF mutations could have a predictive/prognostic value. PATIENTS AND METHODS We retrospectively analyzed objective tumor responses, time to progression, overall survival (OS), and the mutational status of KRAS and BRAF in 113 tumors from cetuximab- or panitumumab-treated metastatic CRC patients. The effect of the BRAF V600E mutation on cetuximab or panitumumab response was also assessed using cellular models of CRC. Results KRAS mutations were present in 30% of the patients and were associated with resistance to cetuximab or panitumumab (P = .011). The BRAF V600E mutation was detected in 11 of 79 patients who had wild-type KRAS. None of the BRAF-mutated patients responded to treatment, whereas none of the responders carried BRAF mutations (P = .029). BRAF-mutated patients had significantly shorter progression-free survival (P = .011) and OS (P < .0001) than wild-type patients. In CRC cells, the introduction of BRAF V600E allele impaired the therapeutic effect of cetuximab or panitumumab. Treatment with the BRAF inhibitor sorafenib restored sensitivity to panitumumab or cetuximab of CRC cells carrying the V600E allele. CONCLUSION BRAF wild-type is required for response to panitumumab or cetuximab and could be used to select patients who are eligible for the treatment. Double-hit therapies aimed at simultaneous inhibition of epidermal growth factor receptor and BRAF warrant exploration in CRC patients carrying the V600E oncogenic mutation.