No sign of treatment-induced cardiotoxicity in breast cancer patients
Long-term heart-specific mortality among 347 476 breast cancer patients treated with radiotherapy or chemotherapy: a registry-based cohort study
Introduction and Methods
Improvements in radiotherapy and chemotherapy treatment have resulted in increased survival in breast cancer patients, but there are concerns about treatment-induced long-term mortality due to decline in left ventricular ejection fraction and cardiac disease. Recent data showed that in breast cancer patients, the cumulative mortality due to CVD is higher compared with the cumulative mortality due to the underlying breast cancer disease [1,2]. However these data did not include comparisons with CV mortality in the general population .
In this registry-based retrospective cohort study, the long-term heart-specific mortality was assessed in 347,476 US female breast cancer patients treated with radiotherapy or chemotherapy. Competing risks were taken into account, and a comparison with the general US female population was done.
For this purpose, the Surveillance, Epidemiology, and End Results-18 (SEER-18) database was used that includes 18 regional cancer registries throughout the USA . For the present analysis, women aged ≥15 years with a first primary malignant breast cancer diagnosis between 1 January 2000 and 31 December 2011, treated with chemotherapy or radiotherapy, and a known status of stage, surgery and a known cause of death were identified. The primary endpoint was CV mortality.
- The median follow-up time for patients treated with radiotherapy or chemotherapy was 8.4 years (IQR: 5.5–11.6).
- The conditional standard mortality ratios (cSMRs) for heart-specific mortality in breast cancer patients were decreased compared with the general population (cSMR: 0.84; 95%CI: 0.79-0.90; P<0.0001).
- The cSMRs for all-cause mortality was increased in breast cancer patients compared with the general population (cSMP: 1.12; 95%CI: 1.09–1.15; P <0.0001).
- Younger breast cancer patients (55-59 years) had a 2-fold increase of all-cause mortality compared with the general population (cSMR: 2.25; 95%CI: 1.99–2.53; P <0.0001), which decreased gradually with increasing age.
- Heart-specific mortality increased with age, stage, and with black ethnicity.
- Subgroup analysis showed no difference in heart-specific mortality for human epidermal growth factor 2 (HER2)-positive receptor status compared to HER2-negative receptor status.
In breast cancer patients treated with radiotherapy or chemotherapy, the heart-specific mortality was not increased compared with the general female population, suggesting no treatment-induced cardiotoxicity in these patients.