Is immunotherapy toxicity associated with improved overall survival among older adults with advanced cancer?

Abstract

6580 Background: There is growing evidence that checkpoint inhibitor immunotherapy (IO) toxicity is associated with improved treatment response. There is a paucity of evidence examining the relationship between toxicity and overall survival (OS) in older adults. Methods: We performed a single institution retrospective cohort study of adults who received IO for advanced cancer from 2011-2017. Baseline clinical characteristics were abstracted from the electronic health record. Immune-related toxicities were graded by physicians based on Common Terminology for Adverse Events criteria, v4.0. Bivariate analysis with chi-squared statistics was used to describe baseline characteristics of patients ≥70 years (y) vs. <70y. Survival outcomes were estimated by the Kaplan-Meier method (time zero = start of first-line IO) and compared using the log-rank test. The association of age and ≥ grade 3 toxicity with OS was tested with a Cox proportional hazards model. Results: Among 676 patients treated with IO, 238 (35.4%) were ≥70y. There was no difference in baseline characteristics of each age group except cancer type (P<0.01). The incidence of ≥ grade 3 toxicity did not differ by age (<70y: 14.5% vs. ≥70y: 13.5%, P=0.71). Median OS was significantly longer for adults <70y (16.4 vs. 13.2 months, P<0.01) or those with ≥ grade 3 toxicity (18.3 vs. 14.7 months, P<0.01). When stratified by age and toxicity, patients <70y with ≥ grade 3 toxicity had longer OS vs. those without ≥ grade 3 toxicity (P<0.01). However, there was no OS difference among adults ≥70y with vs. without ≥ grade 3 toxicity (P=0.78). Adjusted hazard ratios with an interaction term are below. Conclusions: Though the incidence of ≥ grade 3 toxicity did not significantly differ by age, there was no significant OS advantage for older adults with ≥ grade 3 toxicity as compared to younger adults. Caution should be used in considering a toxicity-survival relationship in older adults.[Table: see text]