Breast cancer: the cardioprotective effect of exercise during treatment remains uncertain

Seven trials, but only two could be pooled

The researchers gathered seven randomized trials, comprising nine publications and 513 participants. These studies compared a structured exercise program with usual care in women receiving anthracyclines and/or anti-HER2 therapy for breast cancer.

The review examined left ventricular ejection fraction, global longitudinal strain of the heart, and cardiac biomarkers. The main synthesis was limited to the period from the start to the end of anthracycline treatment, approximately four months. Only two trials were sufficiently comparable for their results to be pooled quantitatively.

No difference detected in cardiac measurements

Ejection fraction indicates the proportion of blood pumped out by the left ventricle with each contraction. Global longitudinal strain measures the deformation of the heart muscle during contraction. These are measures of cardiac function, not clinical outcomes such as hospitalization or survival.

For these two measures, the pooled analysis detected no difference between the exercise and usual-care groups. However, the confidence intervals remained compatible with a benefit, no effect, or an adverse effect. Saying that exercise does not protect the heart would therefore be more categorical than the data allow.

The biomarker results were too heterogeneous to be pooled in a meta-analysis. They cannot provide a reliable overall estimate to help answer the question.

Prevention of complications remains an unanswered question

The trials did not report comparative clinical outcomes for cardiovascular events or survival. Nor did they include a formal assessment of heart failure with preserved ejection fraction. The review therefore does not allow a conclusion that exercise reduces these complications.

Most trials had methodological concerns or a high risk of bias. With only two trials pooled, the conclusion depends on a small portion of the available data. The authors describe the evidence as sparse, heterogeneous, and of low certainty.

What this review changes

This review highlights the need to distinguish exercise during treatment from a specific promise of cardioprotection. The available data do not justify presenting an exercise program as proven protection against the cardiac effects of these treatments.

It does not settle the question of other possible benefits of physical activity or provide a protocol to follow. If you are undergoing treatment, this finding alone is not enough to decide on your own whether to start, modify, or stop a program: that decision should be discussed with your care team.

What we can take away

The cardioprotective effect of exercise during these breast cancer treatments is not confirmed. Uncertainty also extends to cardiovascular complications and survival, because comparative outcomes are lacking.