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

TLDR

The study assessed atypical response patterns and the association between overall survival and best overall response measured by irRC and RECIST v1.1 in advanced melanoma patients treated with pembrolizumab in the phase Ib KEYNOTE‑001 trial. Using centrally adjudicated irRC and RECIST v1.1 data from patients with ≥28 weeks of imaging, the authors defined pseudoprogression as a ≥25 % tumor burden increase at week 12 or later that was not confirmed as progressive disease at the next assessment, and evaluated responses in 327 of 655 enrolled patients. Among 327 patients, 7 % exhibited atypical responses (15 early, 9 delayed), 14 % progressed per RECIST but not per irRC, and two‑year overall survival was 77.

Abstract

We evaluated atypical response patterns and the relationship between overall survival and best overall response measured per immune-related response criteria (irRC) and Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST v1.1) in patients with advanced melanoma treated with pembrolizumab in the phase Ib KEYNOTE-001 study (clinical trial information: NCT01295827).Patients received pembrolizumab 2 or 10 mg/kg every 2 weeks or every 3 weeks. Atypical responses were identified by using centrally assessed irRC data in patients with ≥ 28 weeks of imaging. Pseudoprogression was defined as ≥ 25% increase in tumor burden at week 12 (early) or any assessment after week 12 (delayed) that was not confirmed as progressive disease at next assessment. Response was assessed centrally per irRC and RECIST v1.1.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.