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

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.

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.

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.

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.