Multinational phase 3 trial of first-line retifanlimab plus chemotherapy for advanced squamous anal cancer: final outcomes from POD1UM-303/InterAACT-2

In the multinational phase 3 POD1UM-303/InterAACT-2 trial, adult patients with systemic treatment-naïve advanced/metastatic squamous cell carcinoma of the anal canal (SCAC) were randomized to retifanlimab (n=154) or placebo (n=154, both with carboplatin-paclitaxel chemotherapy. Crossover to retifanlimab monotherapy was permitted on progression in the placebo group. Primary analysis of the trial showed improved median progression-free survival in the retifanlimab group. Final survival outcomes from the trial have now been published. A total of 77 patients crossed over to retifanlimab. In the updated analysis, both progression-free survival (HR 0.62; 95% CI 0.47-0.81) as well as overall survival (0.75; 0.55-1.01) were longer in the retifanlimab group; median OS was 32.8 versus 22.2 months. Overall response rate was 56.5% versus 44.8%, and disease control rates were 87.7% versus 80.5%. Results of the crossover-adjusted analysis were consistent with the main analysis; there was a consistent OS benefit with retifanlimab in all subgroups analyzed. No new safety signals were reported. The authors conclude that this final analysis confirms the benefit of retifanlimab plus chemotherapy in SCAC.