Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST v1.1) may underestimate the treatment response in patients with advanced melanoma treated with pembrolizumab , a study published in the Journal of Clinical Oncology has shown.1

In this study, researchers sought to evaluate the atypical response patterns and the relationship between overall survival and best overall response measured using immune-related response criteria (irRC) and RECIST v1.1.

Centrally assessed irRC data was used to identify atypical responses in patients who underwent 28 or more weeks of imaging. For the study, pseudoprogression was defined as 25% or greater increase in tumor burden at week 12 (early) or any assessment after week 12 (delayed) that was not confirmed as progressive disease at the next assessment. Response was assessed centrally per irRC and RECIST v1.1.

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The study included 655 patients with advanced melanoma enrolled in the phase Ib KEYNOTE-001 study ( NCT01295827). Participants received pembrolizumab 2 or 10 mg/kg every 2 weeks or every 3 weeks. Imaging follow-up for 28 or more weeks was performed in 327 patients, of whom atypical responses were seen in 24 (7%):  early pseudoprogression in 15 (5%) patients and delayed pseudoprogression in 9 (3%) patients.

In 84 of 592 patients (14%) who survived 12 weeks or longer, disease was defined as progressive with RECIST v1.1, but was defined as nonprogressive 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).

The researchers conclude that conventional RECIST may underestimate the benefit of treating advanced melanoma with pembrolizumab for approximately 15% of patients. Premature cessation of treatment may be prevented if modified criteria that permit treatment beyond initial progression are used.


1. Hodi FS, Hwu WJ, Kefford R, et al. Evaluation of immune-related response criteria and RECIST v1.1 in patients with advanced melanoma treated with pembrolizumab [published online ahead of print March 7, 2016]. J Clin Oncol. doi:10.1200/JCO.2015.64.0391.