Racial Differences in Time to Breast Cancer Surgery and Overall Survival in the US Military Health System

Abstract

Racial disparities in time to surgery (TTS) after a breast cancer diagnosis and whether these differences account for disparities in overall survival have been understudied in the US population. To compare TTS in non-Hispanic black (NHB) and non-Hispanic white (NHW) women with breast cancer and to examine whether racial differences in TTS may explain possible racial disparities in overall survival in a universal health care system. Retrospective cohort identified from the Department of Defense Central Cancer Registry and Military Health System Data Repository linked databases containing records between January 1, 1998, and December 31, 2008, of 998 NHB women and 3899 NHW women who received a diagnosis of stages I to III breast cancer and underwent breast-conserving surgery (BCS) or mastectomy in the US Military Health System during the study period. Data analyses were conducted from July 5, 2017, to December 29, 2017. The main outcome was time to breast cancer surgery. Non-Hispanic black and NHW women were compared at the 25th, 50th (median), 75th, and 90th percentiles of TTS by using multivariable quantile regression. Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% CIs for all-cause death in NHB compared with NHW women after controlling for potential confounders first without and then with TTS. Among the 4887 NHB and NHW women in the cohort, the mean (SD) age was 50.0 (9.4) years. The median TTS was 21 days (95% CI, 20.6-21.4 days) among NHW women and 22 days (95% CI, 20.6-23.4 days) among NHB women. Non-Hispanic black women had a significantly greater estimated TTS at the 75th (3.6 days; 95% CI, 1.6-5.5 days) and 90th (8.9 days; 95% CI, 5.1-12.6 days) percentiles than NHW women in multivariable models. The estimated differences were similar by surgery type. Non-Hispanic black women had a higher adjusted risk for death (HR, 1.45; 95% CI, 1.06-2.01) compared with NHW women among patients receiving breast-conserving surgery. The risks were similar between races among those receiving mastectomy (HR, 1.06; 95% CI, 0.76-1.48). The HRs remained similar after adding TTS to the Cox proportional hazards regression models. This study's results indicate that time to breast cancer surgery was delayed for NHB compared with NHW women in the Military Health System. However, the racial differences in TTS did not explain the observed racial differences in overall survival among women who received breast-conserving surgery.