Maintenance Therapy with Panitumumab Alone vs Panitumumab Plus Fluorouracil-Leucovorin in Patients with RAS Wild-Type Metastatic Colorectal Cancer: A Phase 2 Randomized Clinical Trial

Key PointsQuestionIs maintenance therapy with single-agent panitumumab noninferior to panitumumab plus fluorouracil and leucovorin after a 4-month induction treatment with panitumumab plus FOLFOX-4 in patients with previously untreated RAS wild-type metastatic colorectal cancer? FindingsIn this open-label, phase 2 randomized clinical trial of 229 patients, maintenance therapy with single-agent panitumumab alone was inferior to panitumumab plus fluorouracil-leucovorin in terms of 10-month progression-free survival (49.0% vs 59.9%). MeaningThe continuation of single-agent anti-epidermal growth factor receptor treatment in the maintenance setting will likely achieve inferior progression-free survival compared with the continuation of chemotherapy plus an anti-epidermal growth factor receptor agent in a phase 3 confirmation trial. This open-label, phase 2 randomized clinical trial assesses whether maintenance therapy with single-agent panitumumab was noninferior to panitumumab plus combined fluorouracil and leucovorin calcium among patients with RAS wild-type metastatic colorectal cancer. ImportanceFew studies are available on the role of maintenance strategies after induction treatment regimens based on anti-epidermal growth factor receptors, and the optimal regimen for an anti-epidermal growth factor receptors-based maintenance treatment in patients with RAS wild-type metastatic colorectal cancer is still to be defined. ObjectiveTo determine whether maintenance therapy with single-agent panitumumab was noninferior to panitumumab plus fluorouracil and leucovorin after a 4-month induction treatment regimen. Design, Setting, and ParticipantsThis open-label, randomized phase 2 noninferiority trial was conducted from July 7, 2015, through October 27, 2017, at multiple Italian centers. Patients with RAS wild-type, unresectable metastatic colorectal adenocarcinoma who had not received previous treatment for metastatic disease were eligible. Induction therapy consisted of panitumumab plus FOLFOX-4 (panitumumab, 6 mg/kg, oxaliplatin, 85 mg/m(2) at day 1, leucovorin calcium, 200 mg/m(2), and fluorouracil, 400-mg/m(2) bolus, followed by 600-mg/m(2) continuous 24-hour infusion at days 1 and 2, every 2 weeks). Cutoff date for analyses was July 30, 2018. InterventionsPatients were randomized (1:1) to first-line panitumumab plus FOLFOX-4 for 8 cycles followed by maintenance therapy with panitumumab plus fluorouracil-leucovorin (arm A) or panitumumab (arm B) until progressive disease, unacceptable toxic effects, or consent withdrawal. The minimization method was used to stratify randomization by previous adjuvant treatment and number of metastatic sites. Main Outcomes and MeasuresThe prespecified primary end point was 10-month progression-free survival (PFS) analyzed on an intention-to-treat basis with a noninferiority margin of 1.515 for the upper limit of the 1-sided 90% CI of the hazard ratio (HR) of arm B vs A. ResultsOverall, 229 patients (153 male [66.8%]; median age, 64 years [interquartile range (IQR), 56-70 years]) were randomly assigned to arm A (n=117) or arm B (n=112). At a median follow-up of 18.0 months (IQR, 13.1-23.3 months]), a total of 169 disease progression or death events occurred. Arm B was inferior (upper limit of 1-sided 90% CI of the HR,1.857). Ten-month PFS was 59.9% (95% CI, 51.5%-69.8%) in arm A vs 49.0% (95% CI, 40.5%-59.4%) in arm B (HR,1.51; 95% CI, 1.11-2.07; P=.01). During maintenance, arm A had a higher incidence of grade 3 or greater treatment-related adverse events (36 [42.4%] vs 16 [20.3%]) and panitumumab-related adverse events (27 [31.8%] vs 13 [16.4%]), compared with arm B. Conclusions and RelevanceIn patients with RAS wild-type metastatic colorectal cancer, maintenance therapy with single-agent panitumumab was inferior in terms of PFS compared with panitumumab plus fluorouracil-leucovorin, which slightly increased the treatment toxic effects. Trial RegistrationClinicalTrials.gov identifier: NCT02476045