The proportion of women living with a diagnosis of breast cancer in developed countries is increasing. Because breast cancer-specific deaths decrease with time since diagnosis, it is important to assess the burden of other causes of death in women diagnosed with breast cancer.
Different causes of death within 10 years from diagnosis were assessed in 12,850 women younger than 75 years of age with stage 1 to 3 breast cancer diagnosed in Stockholm and Gotland regions 1990 to 2006. Flexible parametric survival models were used to estimate hazard ratios over time since diagnosis by tumor characteristics and age at diagnosis.
The proportion of deaths attributed to breast cancer ranged from 95.0% among women younger than age 45 years at diagnosis to 44.5% among women age 65 to 74 years. The proportions of circulatory system-specific deaths and deaths resulting from other causes increased with older age at diagnosis. Patients with one to three positive lymph nodes were more likely to die as a result of breast cancer during the first 10 years of follow-up compared with women without positive lymph nodes. Women with estrogen receptor (ER) -positive tumors had the same risk of dying as a result of breast cancer 5 years after diagnosis compared with women with ER-negative tumors.
Lymph node negativity is an important long-term predictor of more favorable prognosis. The nature of the relationship between ER status and risk of dying as a result of breast cancer after 5 years of follow-up requires further investigation. Circulatory system diseases are an important cause of death, especially in women diagnosed with breast cancer at an older age.