MODELING ACCRUAL OF OLDER ADULTS TO CANCER CLINICAL TRIALS: (ALLIANCE A151736)

e18132 Background: Older adults (65+ years) make up > 50% of cancer patients in the US,1 yet, older patient enrollment onto trials remains < 30%.2 This study’s aim was to determine the association between trial level variables and accrual rates of adults 65+ to better design trials that can more improve enrollment of these patients. Methods: We analyzed enrollment percentages of patients age 65+ in non-age specific Alliance trials with > 50 patients, that completed accrual between 1995- 2015. Enrollment percentage by 65+ for each study was compared to cancer incidence percentage by 65+ according to the Surveillance, Epidemiology, and End Results (SEER) Program for the same time periods. Enrollment Disparity Difference (EDD)3, defined as the difference between SEER incidence percentage of patients 65+ and the trial percentage enrollment of 65+ was calculated for each trial ( SEER % – trial %). Univariate analyses (UVA) were performed using simple linear regression to determine trial variables associated with larger EDDs (higher disparity). Variables that had an F-test p-value < 0.20 were included in a multivariable fixed-effects linear model for multivariate analysis (MVA). Results: Median age of 66,708 patients across 237 trials with 10 cancer types was 60 years. Average % of 65+ in trials was lower than average SEER comparison % 65+ per trial (37.6% vs. 57.8%). The median trial EDD, was 16.7%. On UVA, cancer type was significantly associated with higher EDD (see Table). Use of fewer modalities (1, 2, vs 3+) was associated with lower estimated EDDs (1 = -11 [+/-3.6], 2 = -8.9 [+/-3.9], F-test p = .012). On MVA, non-genitourinary (GU) cancer type, number of treatment modalities, and the phase (II or III compared to observational/other) were all significantly associated with higher EDD. Conclusions: Older adults were under-represented in this large sample of trials. This information can be used as a platform to better design disease-specific trials to improve older patient accrual, particularly in disease areas which are under-performing. Support: U10CA180821, U10CA180882, UG1CA189823: https://acknowledgments.alliancefound.org . References: 1. Smith BD et al. J Clin Oncol 27:2758-65, 2009; 2. Hurria A, et al. J Geriatr Oncol 1:40-44, 2010; 3. Pang HH, et al. J Clin Oncol, 2016.[Table: see text]