Comparison of RECIST, iRECIST, and PERCIST for the Evaluation of Response to PD-1/PD-L1 Blockade Therapy in Patients With Non-Small Cell Lung Cancer.

Purpose: The aim of this study was to compare the Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, the immune RECIST (iRECIST) criteria, and the Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST) 1.0 in patients with advanced non-small cell lung cancer treated with programmed cell death protein 1 (PD-1)/programmed cell death protein 1 ligand (PD-L1) inhibitors.

Methods: This prospective study of 42 patients treated with a PD-1/PD-L1 inhibitor was approved by our institutional review board, and all patients gave written, informed consent. Tumor burden dynamics were assessed on F-FDG PET/CT before and after treatment initiation. Immunotherapeutic responses were evaluated according to RECIST 1.1, iRECIST, and PERCIST 1.0 for the dichotomous groups, responders versus nonresponders. Cohen κ and Wilcoxon signed rank tests were used to evaluate concordance among these criteria. We assessed progression-free survival and overall survival using the Kaplan-Meier estimator.

Results: The RECIST 1.1 and PERCIST 1.0 response classifications were discordant in 6 patients (14.2%; κ = 0.581). RECIST 1.1 and iRECIST were discordant in 2 patients, who evidenced pseudoprogression after treatment initiation. Median progression-free survival, as well as overall survival, was significantly longer for responders compared with nonresponders for all criteria (P < 0.001), with no significant difference between the 3 criteria (P > 0.05).

Conclusions: RECIST 1.1 and PERCIST 1.0 show only moderate agreement, but both can predict treatment response to PD-1/PD-L1 inhibitor therapy. In case of pseudoprogression, metabolic tumor activity may help to correctly classify treatment response.