Purpose: Delays in adjuvant breast cancer (BC) therapy have been shown to worsen outcomes. However, thus far studies have only evaluated delays to initial treatment, or a particular modality, such as chemotherapy, leaving uncertainty about the role of delay to subsequent therapy and the effects of cumulative delay, on outcomes. We investigated the associations of delays across treatment modalities with survival.
Methods: We included 3368 women with incident stage I-III BC in the Women's Health Initiative (WHI) enrolled in fee-for-service Medicare who underwent definitive surgery. This prospective analysis characterized treatment delays by linking WHI study records to Medicare claims. Delays were defined as > 8 weeks to surgery, chemotherapy, and radiation from diagnosis or prior treatment. We used Cox proportional hazards models to estimate BC-specific mortality (BCSM) and all-cause mortality (ACM) in relation to treatment delays.
Results: We found 21.8% of women experienced delay to at least one therapy modality. In adjusted analysis, delay to chemotherapy was associated with a higher risk of BCSM (HR = 1.71; 95% CI 1.07-2.75) and ACM (HR = 1.39; 95% CI 1.02-1.90); delay in radiation increased BCSM risk (HR = 1.49; 95% CI 1.00-2.21) but not ACM risk (HR = 1.19; 95% CI 0.99-1.42). Delays across multiple treatment modalities increased BCSM risk threefold (95% CI 1.51-6.12) and ACM risk 2.3-fold (95% CI 1.50-3.50).
Conclusions: A delay to a single treatment modality and delay to a greater extent an accumulation of delays were associated with higher BCSM and ACM after BC. Timely care throughout the continuum of breast cancer treatment is important for optimal outcomes.
Keywords: Adjuvant breast cancer; Breast cancer-specific mortality; Chemotherapy; Radiation; Survival; Treatment delay.