ASPO Abstracts
Trends in heart disease mortality among US breast cancer survivors, from 1975-2017
Category: Survivorship & Health Outcomes/Comparative Effectiveness Research
Conference Year: 2021
Abstract Body:
Purpose of the study: Heart disease is a significant concern among breast cancer survivors, in part
due to cardiotoxic treatments including chemotherapy and radiotherapy.
Methods: We examined trends in heart disease mortality among first primary invasive breast
cancer survivors diagnosed between 1975-2016 (aged 18-84; survived 12+ months; received
initial chemotherapy, radiotherapy, or surgery) in the US Surveillance, Epidemiology, and End
Results database. Standardized mortality ratios (SMRs) comparing heart disease mortality among
breast cancer survivors to the US general population and 10-year cumulative heart disease
mortality estimates accounting for competing events were calculated by calendar year of
diagnosis, treatment type, and stage.
Results: Of 516,916 breast cancer survivors, 40,812 died of heart disease through 2017 (median
follow-up time=11.3y). Overall, SMRs of heart disease declined by calendar year of diagnosis from
1975-2016 (SMR 1.01[95%CI 0.98,1.03] to 0.74[0.69,0.79], ptrend<.001). A similar declining trend
was observed for radiotherapy (ptrend<.001), chemotherapy with radiotherapy (ptrend<.001), and
nonsignificant decline for surgery alone (ptrend=.18). A sharper decline was observed from 1975-
1989 for left-sided radiotherapy, compared to right-sided, and similar declines from 1990-2016.
Declining trends were evident among all stages for radiotherapy, localized and regional cancers for
chemotherapy with radiotherapy, and localized cancers for surgery alone. In contrast, there was an
increasing trend in SMRs for chemotherapy (SMR 0.88[95%CI 0.77,0.99] to 1.01[0.81,1.25],
ptrend=.008), especially for regional stage. The 10-year cumulative mortality estimates were
7.12%[95%CI 7.00,7.24] for surgery alone, 1.90%[1.76,1.98] for chemotherapy, 1.37%[1.29,1.46]
for chemotherapy with radiotherapy, and 4.56%[4.44,4.69] for radiotherapy.
Conclusions: We observed declining trends in heart disease mortality overall and by most
treatment types, yet increasing for chemotherapy users, highlighting a need for additional studies
with detailed treatment data. Improved cardioprotection strategies in modern radiotherapy may
have contributed to declines in heart disease mortality. Understanding the impact of treatment on
heart disease mortality is crucial.
Keywords: breast cancer; survivorship; heart disease risk; descriptive epidemiology