Evaluation of Immune-Related Response Criteria and RECIST v1.1 in Patients With Advanced Melanoma Treated With Pembrolizumab

Of the 655 patients with melanoma enrolled, 327 had ≥ 28 weeks of imaging follow-up. Twenty-four (7%) of these 327 patients had atypical responses (15 [5%] with early pseudoprogression and nine [3%] with delayed pseudoprogression). Of the 592 patients who survived ≥ 12 weeks, 84 (14%) experienced progressive disease per RECIST v1.1 but nonprogressive disease per irRC. Two-year overall survival rates were 77.6% in patients with nonprogressive disease per both criteria (n = 331), 37.5% in patients with progressive disease per RECIST v1.1 but nonprogressive disease per irRC (n = 84), and 17.3% in patients with progressive disease per both criteria (n = 177).

Atypical responses were observed in patients with melanoma treated with pembrolizumab. Based on survival analysis, conventional RECIST might underestimate the benefit of pembrolizumab in approximately 15% of patients; modified criteria that permit treatment beyond initial progression per RECIST v1.1 might prevent premature cessation of treatment.