Racial and ethnic differences in colorectal cancer screening effectiveness in the PLCO trial.

Abstract

e15687 Background: Colorectal cancer (CRC) screening has been shown to reduce CRC-related mortality, yet substantial racial and ethnic disparities persist. Whether CRC screening confers equivalent mortality benefit across racial and ethnic groups, and the mechanisms underlying potential heterogeneity if any, remains unelucidated. Methods: We conducted a secondary analysis of the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial, including 154,852 participants aged 55–74 years randomized to CRC screening or usual care. After excluding those with incomplete diagnostic data, 2,123 were eligible for analyses (929 in the screening arm, 1,195 in the control arm). Primary outcomes included cumulative incidence and CRC-specific mortality. Age-adjusted CRC mortality rates (AR, per 100,000) and crude rates (CR) were estimated by race/ethnicity and trial arm. Effect heterogeneity was assessed descriptively with trial-center analyses given correlations between center and racial/ethnic composition. Results: Overall, CRC screening was associated with lower cumulative CRC incidence and CRC-specific mortality compared with usual care. However, the magnitude of mortality reduction varied substantially by race/ethnicity (Table). Trial-center analyses demonstrated wide heterogeneity and screening–control separation across. For instance, data from Pennsylvania and Hawaii centers which has a high proportion of either non-Hispanic Black participants or Native Hawaiian/Pacific Islanders, had no mortality separation after 20 years of follow-up. Conclusions: Within a large randomized trial data, CRC screening effectiveness on mortality was not uniform across racial and ethnic groups. To enhance CRC screening benefits and to address the racial differences, downstream care processes have to be optimized rather than focusing on screening exposure alone. Future prospective data is warranted to address inequities in the full screening-to-diagnosis-to-treatment continuum and find out in which stage of care a care delivery disruption occurs. Colorectal cancer mortality by race/ethnicity and screening arm in the PLCO trial. Race/Ethnicity Age-standardized Mortality Rate per 100,000 (95% CI)　 Risk Reduction (95% CI) Screening Control Absolute Relative (%) White 362.1(313.8–410.3) 538.5(479.4–597.6) 176.4(100.1–252.7) 32.8(20.1–43.4) Black 680.8(405.8–955.7) 808.6(499.1–1118.2) 127.9(-286.2–541.9) 15.8(-46.9–51.7) Hispanic 455.8(86.7–824.8) 654.3(198.2–1110.4) 198.5(-388.2–785.3) 30.3(-102.8–76.1) Asian 333.0(84.7–581.2) 588.2(252.3–924.0) 255.2(-162.4–672.9) 43.4(-44.8–77.9)