Background: Due to improved outcomes in breast cancer (BCa), the proportion of affected women dying of other causes has increased. Thus, a better survival of BCa requires knowledge of other causes of death.
Materials and methods: Data on the population, cancers, and causes of death were gathered from the nationwide Swedish Family-Cancer Database, enrolling ∼3.68 million Swedish women. A Cox regression model, comparing BCa patients against all other women, was applied. Cause-of-death-specific hazard ratios (HRs) were calculated for both underlying and multiple causes of death.
Results: Among 641 000 deaths from 1987 to 2006, 48,000 were BCa patients. For underlying causes except BCa, the highest cause-specific HRs were found for diseases of pulmonary circulation {1.51 [95% confidence interval (CI) 1.36-1.68]}, suicide [1.39 (1.19-1.63)], and heart failure [1.29 (1.22-1.37)]. For specific multiple causes, the highest ratios were found for external causes [1.86 (1.80-1.91)] and gastrointestinal disease [1.68 (1.62-1.74)].
Conclusions: Diagnosis of BCa is associated with increased risks of dying of various causes, including external causes, heart failure, diseases of pulmonary circulation, and gastrointestinal disease. The study fulfills the gap in knowledge of death causes in BCa patients and suggests to draw more attention to comorbidities.