Purpose: We aimed to report the 20-year risk of breast cancer-specific mortality (BCSM), report the risk of BCSM conditional on having survived 5 years, and identify factors associated with late deaths in stage III breast cancer.
Methods: Using Surveillance, Epidemiology, and End Results data, we included women with stage III breast cancer diagnosed from 1990 to 2005. We excluded women with unknown hormone receptor (HR) status, women who did not undergo resection of the primary tumor or axillary nodes, or unknown cause of death. We estimated risks of BCSM using cumulative incidence function and used Fine and Gray regression to identify factors associated with late deaths.
Results: Final sample was 36,500 patients with 14 years of median follow-up. For each stage subgroup, the risk of BCSM at 20 years was significantly higher for HR-negative vs HR-positive tumors (IIIA: 49.8% vs 43.2%, P < 0.0001; IIIB: 60.9% vs 47.6%, P < 0.0001; IIIC: 68.7% vs 63.1%, P < 0.0001). Compared with the risks of non-BCSM, the risks of BCSM at 20 years were four times higher in stage IIIC HR-positive disease and seven times higher in stage IIIC HR-negative disease. Risks of BCSM conditional on having survived 5 years depended on tumor size, nodal status, race, and tumor grade for HR-positive disease and depended on tumor size, nodal status, and age for HR-negative disease.
Conclusions: In stage III breast cancer, the risk of BCSM at 20 years is very high and remains important even beyond the first 5 years in both HR-positive and HR-negative disease. Late BCSM depends on traditional clinicopathologic factors.