Weberpals J, et al. - In a large cohort of breast cancer patients, researchers looked for competing causes of death and prognostic factors in order to define the heart-specific mortality in relation to the general population. Relative to the general population, breast cancer survivors did not have increased heart-specific mortality. No increased heart-specific mortality was observed among human epidermal growth factor receptor 2 (HER2)-positive patients vs HER2-negative patients.

Methods

• This was a registry-based cohort study, which included 347,476 eligible breast cancer patients.
• Researchers used the Surveillance, Epidemiology, and End Results-18 (SEER-18) database to identify women diagnosed with breast cancer between 2000 and 2011 who were treated with radiotherapy or chemotherapy and followed until 2014.
• Long-term (≥10 years) standardized mortality ratios (SMRs) were calculated to determine heart-specific mortality relative to the general population. Cumulative mortality functions were also computed.
• Cause-specific hazard ratios (HRcs) were calculated with corresponding 95% confidence intervals using the Cox proportional hazards regression to assess prognostic factors for heart-specific mortality.
• They also carried out subgroup analysis on intermediate-term mortality according to molecular subtypes, for which information was available since 2010.

Results

• The highest cumulative mortality was attributed to breast cancer among all possible competing causes of death.
• Relative to the general population, lower heart-specific mortality was noted in breast cancer patients treated with radiotherapy or chemotherapy [SMR_overall 0.84 (0.79–0.90)].
• In subgroup analysis, human epidermal growth factor receptor 2 (HER2)-positive subtype was not shown to be related to increased heart-specific mortality, compared with HER2-negative patients [HRcs 0.96 (0.70–1.32)].