Panitumumab versus cetuximab in patients with chemotherapy-refractory wild-type KRAS exon 2 metastatic colorectal cancer (ASPECCT): a randomised, multicentre, open-label, non-inferiority phase 3 study

Summary Background The anti-EGFR monoclonal antibodies panitumumab and cetuximab are effective in patients with chemotherapy-refractory wild-type KRAS exon 2 metastatic colorectal cancer. We assessed the efficacy and toxicity of panitumumab versus cetuximab in these patients. Methods For this randomised, open-label, phase 3 head-to-head study, we enrolled patients (from centres in North America, South America, Europe, Asia, Africa, and Australia) aged 18 years or older with chemotherapy-refractory metastatic colorectal cancer, an Eastern Cooperative Oncology Group (ECOG) performance status of 2 or less, and wild-type KRAS exon 2 status. Using a computer-generated randomisation sequence, we assigned patients (1:1; stratified by geographical region and ECOG performance status, with a permuted block method) to receive panitumumab (6 mg/kg once every 2 weeks) or cetuximab (initial dose 400 mg/m2 ; 250 mg/m2 once a week thereafter). The primary endpoint was overall survival assessed for non-inferiority (retention of ≥50% of the cetuximab treatment effect; historical hazard ratio [HR] for cetuximab plus best supportive care vs best supportive care alone of 0·55). The primary analysis included patients who received one or more dose of panitumumab or cetuximab, analysed per allocated treatment. Recruitment for this trial is closed. The trial is registered with ClinicalTrials.gov , number NCT01001377. Findings Between Feb 2, 2010, and July 19, 2012, we enrolled and randomly allocated 1010 patients, 999 of whom began study treatment: 499 received panitumumab and 500 received cetuximab. For the primary analysis of overall survival, panitumumab was non-inferior to cetuximab ( Z score −3·19; p=0·0007). Median overall survival was 10·4 months (95% CI 9·4–11·6) with panitumumab and 10·0 months (9·3–11·0) with cetuximab (HR 0·97; 95% CI 0·84–1·11). Panitumumab retained 105·7% (81·9–129·5) of the effect of cetuximab on overall survival seen in this study. The incidence of adverse events of any grade and grade 3–4 was similar across treatment groups. Grade 3–4 skin toxicity occurred in 62 (13%) patients given panitumumab and 48 (10%) patients given cetuximab. The occurrence of grade 3–4 infusion reactions was lower with panitumumab than with cetuximab (one [