Pseudoprogression in cancer immunotherapy: Rates, time course and patient outcomes.

Abstract

6580Background: Pseudoprogression (PP), tumor growth from treatment effect rather than true disease progression, has been described with immune checkpoint inhibitors. Our study measures rates and time course of PP and associated patient outcomes using RECIST 1.1 and irRC criteria. Methods: Cohort was retrospectively drawn from subjects enrolled in phase I and II trials from March 2008 to July 2015 at two hospitals within one cancer center network. Inclusion required followup with every 4-12 week scheduled torso CT or MRI for > 1 year or until death analyzed using RECIST 1.1 and irRC criteria by the imaging core lab. A single investigator blinded to patient outcome abstracted the core lab database; another blinded to imaging assessment abstracted patient survival from the medical record. Pattern of response during the first year of therapy assessed according to RECIST 1.1 and irRC criteria were categorized as stable (SD), partial response (PR), progressive disease (PD) or pseudoprogression (PP). PP was def...