Cause-specific mortality in women with breast cancer in situ.

The long-term mortality remains unknown in women diagnosed with breast cancer in situ (BCIS). Here, we assessed the cause-specific mortality in BCIS patients. This population-based cohort study included 12,243 women diagnosed with BCIS in Sweden between 1980 and 2011. Patients were followed until death, emigration, or 31 December 2013, whichever came first. The 30-year cumulative incidence of breast cancer-specific mortality was 6.3%, which is considerably lower than 49.7% observed for other-cause mortality. Women diagnosed with BCIS were more likely to die from breast cancer (standardized mortality ratio [SMR], 3.85; 95% CI, 3.47-4.27) but less likely to die from cardiovascular disease (SMR, 0.88; 95% CI, 0.82-0.95) than women in the general population. Specifically, the SMRs for breast cancer-specific mortality decreased over time from 5.19 (95% CI, 3.95-6.81) among BCIS diagnosed during 1980-1989 to 3.03 (95% CI, 2.35-3.91) among those diagnosed during 2000-2011. Furthermore, higher risk of death from other causes was seen among those with older age at BCIS diagnosis, lower levels of education, nulliparity, higher Charlson Comorbidity Index, and being hospitalized before BCIS diagnosis; whereas, lower risk of death from breast cancer was seen among BCIS diagnosed in the later time period and those with younger age at first birth. We conclude that most women diagnosed with BCIS die from causes other than breast cancer, which highlights the need for actions not only to reduce nonbreast cancer mortality but also to identify patient where extensive curative BCIS treatment is not adding to survival.