Incident Myocardial Infarction, Heart Failure, and Oncologic Outcomes in Breast Cancer Survivors

Background

Cardiovascular disease (CVD) is associated with higher rates of incident cancer. Data are scarce regarding the association of incident CVD with oncologic outcomes after a cancer diagnosis.

Objectives

This study sought to determine whether incident myocardial infarction (MI) or heart failure (HF) in breast cancer survivors is associated with oncologic outcomes.

Methods

This was a population-based cohort study in Ontario, Canada, using linked administrative data sets of women diagnosed with first breast cancer between April 1, 2007, and March 31, 2015. A landmark analysis was conducted of women alive 2 years after breast cancer diagnosis, aged ≥40 years, and with available staging data and without recurrent/distant disease or preceding CVD. The exposure was a composite of MI and/or HF after the landmark date. The outcomes were cancer mortality, new non-breast malignancy diagnosis, and new chemotherapy initiation. Multivariable cause-specific hazards regression was used to determine the association of incident MI/HF (time-varying exposure) with outcomes.

Results

A total of 30,694 women (median age of 60 years) were included, of whom 1,346 developed incident MI/HF at a median of 3.9 years after the landmark date. At 5 years, the cumulative incidence was 5.9% (95% CI: 5.6%-6.1%) for cancer death, 4.3% (95% CI: 4.1%-4.6%) for non-breast malignancy, and 25.7% (95% CI: 25.2%-26.2%) for new chemotherapy. Incident MI/HF was associated with a higher hazard of cancer death (HR: 3.94; 95% CI: 3.38-4.59), non-breast malignancy (HR: 1.39; 95% CI: 1.06-1.82), and new chemotherapy (HR: 1.25; 95% CI: 1.02-1.53).

Conclusions

Incident MI and/or HF after breast cancer treatment are associated with higher hazards of adverse oncologic outcomes, highlighting the need to prioritize care for these patients.