Cemiplimab (PD-1) + response-adapted definitive RT delivers 86% 18-mo EFS in unresectable LA cSCC (RAMPART)

Cemiplimab-rwlc is an anti–PD-1 monoclonal antibody; in RAMPART (Phase II, multicenter, single-arm; NCT05574101), it was given neoadjuvantly (2 doses then response-adapted), concurrently with definitive radiotherapy (50–70Gy in 25–35 fractions; 70Gy/35 if early PD), and as adjuvant therapy up to 1 year for locally advanced unresectable cutaneous squamous cell carcinoma (T3–4 and/or N+, M0). In 34 patients (median age 77; 91% head/neck; 56% recurrent), 18-month EFS from cemiplimab start was 86% (one-sided 95% CI lower bound 73%); 18-month PFS and OS were each estimated at 86% and 92% with 18-month median follow-up—numerically well above historical definitive RT-era benchmarks around ~38% 18-month PFS, and above anti–PD-1-alone outcomes cited around ~55% 18-month PFS in patients not eligible for curative RT/surgery. Safety was described as consistent with known cemiplimab and RT toxicities (no new safety signal reported); most patients completed planned neoadjuvant dosing (85% completed 4 doses) and RT (94%).