Exercise during anthracyclines: a troponin signal, and nothing on function

Design

Systematic review and meta-analysis of randomised controlled trials of exercise interventions of 12 weeks or longer

Population

360 women with breast cancer receiving anthracycline-based chemotherapy across six randomised trials

Primary outcome

Markers of cancer therapy-related cardiac dysfunction: ejection fraction, global longitudinal strain, troponin I and T, NT-proBNP

Effect

Troponin I SMD −0.50 (95% CI −0.93 to −0.06, p = 0.02); no difference in ejection fraction, strain, troponin T or NT-proBNP

Six randomised trials with 360 women receiving anthracycline-based chemotherapy for breast cancer were pooled, restricted to exercise programmes lasting at least 12 weeks with at least one session a week, against usual care. The only outcome that separated was cardiac troponin I, attenuated with exercise, SMD −0.50 (95% CI −0.93 to −0.06, p = 0.02). Left ventricular ejection fraction, global longitudinal strain, troponin T and NT-proBNP all showed no between-group difference.

Troponin I is a marker of myocyte injury, not a measure of cardiac function, and one positive surrogate among five outcomes tested in 360 patients is a weak basis for a claim of cardioprotection. Global longitudinal strain is the more sensitive functional measure here, and it did not move. The authors' own conclusion — that the cardioprotective role remains uncertain — is the correct one.

None of that argues against exercise. It argues against selling exercise on a cardiac protection claim that the evidence does not carry, when the reasons to recommend it during chemotherapy are already good: fatigue, deconditioning, mood, treatment completion. Prescribe it for those, keep the surveillance echocardiography protocol unchanged, and do not let an exercise programme substitute for cardiology review in a patient whose strain is falling.

• Recommend exercise during anthracycline chemotherapy for fatigue and function — not as cardioprotection.
• Do not alter cardiac surveillance intervals on the strength of an exercise programme.
• Keep the referral threshold for cardio-oncology where it is; falling global longitudinal strain still warrants it.
• Twelve weeks at one or more sessions a week is the dose actually studied.
• Troponin I is an injury marker; a smaller rise is not the same as preserved cardiac function.

The statistics, in plain English

A standardised mean difference of −0.50 with an interval of −0.93 to −0.06 barely excludes zero; the upper bound is close enough to no effect that a single additional trial could move it across. That result also stands alone among five outcomes, and testing five outcomes in 360 patients makes one nominally significant finding roughly what chance would produce. The stronger evidence is the set of nulls: ejection fraction and global longitudinal strain are what a cardiologist would act on, and neither differed. When a surrogate moves and the functional measures do not, the safe reading is that the surrogate moved.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.