Analysis of patient (pt) withdrawal of consent using 11,993 pts from 58 alliance for clinical trials in oncology trials.

6513 Background: Pt recruitment receives well-deserved attention, but pt retention is also important for trial interpretability and generalizability. We report on trends and predictive factors for withdrawal of pt consent, defined as pt cessation from trial participation for reasons not mandated in the protocol. Methods: Alliance phase II/III trials that enrolled pts during 2013 – 2019 were included. All pts had ≥2 years (yrs) of follow-up. Primary outcome was withdrawn consent (yes; no) within 2 yrs of enrollment. Pt factors included year of enrollment, age, race, ethnicity, and gender. Trial factors included randomization, use of placebo, and use of radiation. Univariable (Uni) and full multivariable (MV) logistic regression models (including all factors from Uni setting) with a Bonferroni p-value correction (p <.004 considered significant) were used. Results: Median age was 62 yrs, with 67% female, 82% White, 9% Black or African American, and 7% Hispanic. 52% of trials were phase II, 5% II/III and 43% III. Common (> 10%) trial categories included 22% experimental therapeutics or rare tumors, 12% gastrointestinal, 12% genitourinary, 12% neuro-oncology and 10% symptom intervention. 78% of trials were randomized, 22% placebo-controlled and 14% used radiation. 1060 (9%) pts withdrew consent within 2 yr of enrollment (range,5.7% -9.8%) during 2013-2019. In Uni models, all trial and pt factors significantly predicted pt withdrawal except age, race, and gender (See table). In MV models, pts of Hispanic origin, and >75 yrs were more likely to withdraw. Trials using radiation had less likelihood of pt withdrawal. Placebo-controlled randomized trials had higher likelihood of withdrawal. Conclusions: Both trial and pt factors contribute to higher rates of pt withdrawal from clinical trials. Understanding these factors will enable investigators to focus on pt education and optimization of trial design to improve pt retention and the overall clinical trial plan. Support: U10CA180821, U10CA180882 [Table: see text]