Comparison of RECIST and iRECIST criteria in patients with advanced lung cancer treated with nivolumab

Background: Systemic therapy in lung cancer is mainstay of treatment as most patients present in advanced stages, with rising importance of new immunotherapy agents. Purpose: To compare the RECIST 1.1 and the immunotherapy Response Evaluation Criteria in Solid Tumors (iRECISTs) criteria for response assessment in lung cancer patients on immunotherapy. To find the incidence of pseudoprogression and associated imaging patterns. Material and Methods: Retrospective study in 28 patients treated with immunotherapy for advanced metastatic NSCLC. End points were progression-free survival (PFS) and overall survival (OS). Response assessments were separately tabulated according to RECIST 1.1 and iRECIST and classified into dichotomous groups of responders and nonresponders. Agreement in assessments between RECIST 1.0 and iRECIST examined using Cohen kappa (kappa) coefficient with 95% confidence intervals. Kaplan-Meier survival analysis was done for PFS and OS. Differences between RECIST 1.1 and iRECIST for both responder and nonresponder were evaluated by the log rank test, Breslow (Generalized Wilcoxon) test, and Tarone-Ware test. Results: Incidence of pseudoprogression was 7% (2/28). The RECIST1.1 and iRECIST were in disagreement in two patients. The agreement between RECIST and iRECIST was almost perfect. The PFS and the OS are significantly longer in duration for responders in comparison to nonresponders for both RECIST and iRECIST and the difference between two assessment criteria is not significant. Conclusion: Although iRECIST aims to monitor treatment more precisely than conventional response criteria, this must be weighed against how infrequent pseudoprogression is and the cost of this therapy, both financially and in the potential delay in changing to a more effective treatment.