Factors associated with late risks of breast cancer-specific mortality in the SEER registry

PURPOSE: Most reports describing the risk of late relapse in breast cancer (BC) have been based on selected patients enrolled into clinical trials. We examined population-based long-term risks of BC-specific mortality (BCSM), the risks of BCSM conditional on having survived 5 years, and factors associated with late BCSM. METHODS: Using SEER, we identified women diagnosed with BC (T1-T2, N0-N2, M0) between 1990 and 2005 with known hormone receptor (HR) status. Kaplan–Meier analyses determined cumulative risks of BCSM. We performed Fine and Gray regression stratified by HR status. RESULTS: We included 202,080 patients (median follow-up of 14.17 years). Of all BC deaths, the proportion that occurred after 5 years was 65% for HR-positive vs 28% for HR-negative (p < 0.001) BC. In HR-positive BC, the cumulative risks of BCSM during years 5–20 were 9.9%, 21.9%, and 38% for N0, N1, and N2 disease. For HR-negative BC, the risks were 7.9%, 12.2%, and 19.9%, respectively. For T1a/b, N0, HR-positive BC, the risk of BCSM was 6 times lower than the risk of non-BCSM. In N2, HR-positive BC, the risk of BCSM was 43% higher than the risk of non-BCSM. In adjusted Fine and Gray models stratified by HR status, the risks of BCSM conditional on having survived 5 years for both HR-positive and HR-negative depended on T-N status, age, and year of diagnosis. In HR-positive, the risks also depended on race and grade. CONCLUSION: The risks of BCSM beyond 5 years, although different, remain important for both HR-positive and HR-negative BC. Strategies to prevent early and late recurrences are warranted. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10549-021-06233-4.