2048 - Rates of Attrition in Black Patients with Prostate Cancer Enrolled in Randomized Controlled Trials: A Pooled Secondary Analysis of RTOG 9601, 9902, 0126, and 0415

M. A. Hamza¹, H. R. R. Cherng¹, K. Sun², P. T. Tran³, S. M. Bentzen³, and M. V. Mishra³; ¹Department of Radiation Oncology, University of Maryland Medical Center, Baltimore, MD, ²Division of Biostatistics and Bioinformatics, University of Maryland Greenebaum Cancer Center, and Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD, ³Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD

Purpose/Objective(s): Black patients (pts) experience higher prostate cancer (PCa) specific mortality, worse outcomes and lower randomized controlled trial (RCT) enrollment rates compared to White pts. Despite efforts to increase recruitment of Black pts to RCTs, more data are required to characterize the impact of racial disparities on subsequent long-term retention and attrition rates once pts are enrolled. We sought to use clinical data to assess whether race is associated with attrition rates in PCa pts enrolled in RCTs. Materials/

Methods: We conducted a pooled secondary analysis of pts enrolled in four phase 3 National Cancer Institute (NCI) radiation-based PCa trials: Radiation Therapy Oncology Group (RTOG) trials 9601, 9902, 0126 and 0415, utilizing data from the NCTN Data Archive. For this analysis, pts were grouped based on self-reported race: Black or African American versus non-Black (including pts identifying as White, Asian, Native Hawaiian, Pacific Islander, Native American, Alaskan Native, or multi-racial). Pts who did not report race were excluded. Chi-squared test was used to analyze differences in age, Zubrod performance status (ZPS) and study arm randomization (SAR, standard vs experimental) across groups. We calculated attrition rates, stratified by race, prior to reaching the studys primary endpoint of overall survival. Estimation of attrition rates was performed using the Kaplan-Meier estimator of the time to last follow-up and with patients reaching the endpoint treated as censored observations, to assess time until dropout or loss to follow-up. Additionally, variables such as race, age, SAR and ZPS were evaluated using multivariate Cox proportional hazards modeling (MVA).
Results: Across the four trials, 3,703 pts with median FU of 8.7 years (95% CI 8.6,8.9) were included for analysis. 553 (14.9%) pts self-reported as Black, while 3150 (85.1%) reported as non-Black. Most pts were between 60-69 years old (42.2%) and had a ZPS of 0 (93.1%). Black and non-Black pts differed in age and ZPS, with Black pts being younger and having worse ZPS (both P<0.001), but not across SAR (P=0.11). Median FU time for Black vs non-Black pts was 7.7 years (95% CI 7.2, 8.0) and 9 years (95% CI 8.7, 9.2) respectively. Time to attrition analysis across race demonstrated significantly higher attrition rates for Black vs non-Black pts (HR 1.45, 95% CI 1.3, 1.6). On MVA, ZPS, and age were statistically significant and race (HR 1.51, 95% CI 1.4, 1.7) continued to be predictive of time to attrition, while SAR did not show a correlation.
Conclusion: Our findings reveal higher attrition rates in Black vs non-Black PCa pts enrolled in phase 3 RCTs. These results highlight the continued need for enhancement of culturally competent interventions to achieve equitable recruitment and retention rates among Black pts. Such efforts are vital to addressing racial disparities and increasing RCT generalizability.