Missing Script

Get updates

Evidence Explorer · MS-N240 · Exercise and rehabilitation · cardiorespiratory fitness and cardiac function · Appraised November 5, 2026

Randomized trials suggest supervised aerobic and resistance exercise can preserve fitness during cardiotoxic breast-cancer treatment and may slightly attenuate left-ventricular ejection-fraction decline. The studies do not establish prevention of clinical heart failure or cancer-treatment-related cardiac dysfunction.

Evidence at a glance

  • Benefit signal: Consistent improvement or preservation of cardiorespiratory fitness; a small ejection-fraction signal in one trial, with no clear biomarker or global-longitudinal-strain benefit.
  • Certainty: Low-to-moderate for fitness; low for clinically meaningful cardioprotection because trials were modest in size and clinical cardiac events were rare.
  • Risk context: Programs were supervised and selected for eligible participants; pretreatment assessment matters when symptoms or cardiovascular disease are present.
  • Cancer-control relevance: Supportive-care evidence only. These trials did not test tumor response, recurrence or survival.

What was studied

In BREXIT, 104 women with stage I–III breast cancer were randomized 1:1 to 12 months of aerobic and resistance exercise, three to four days per week, or usual care during anthracycline-containing treatment.

In ONCORE, 122 women receiving anthracycline and/or anti-HER2 therapy were randomized to a supervised cardio-oncology rehabilitation program (60) or exercise recommendation alone (62), for a mean of 5.8 months.

What the study found

BREXIT did not meet its 12-month primary endpoint for functional disability: odds ratio 0.27 (95% CI 0.06 to 1.12; p=0.07). At four months, functional disability was less frequent (odds ratio 0.32, 95% CI 0.11 to 0.94). Peak oxygen uptake was about 3.5 mL/kg/min higher with exercise; resting left-ventricular function did not differ.

ONCORE reported a 1.5-percentage-point smaller decline in left-ventricular ejection fraction (95% CI 0.1 to 2.9 points; p=0.006), but no cases of treatment-related cardiac dysfunction and no between-group differences in global longitudinal strain or cardiac biomarkers.

What this does not establish

A statistically detectable ejection-fraction difference is not automatically a meaningful reduction in heart failure or later cardiovascular events. Neither trial was powered to establish rare clinical cardiac outcomes, and neither supports changing indicated cancer therapy without oncology and cardiology input.

Safety and practical context

New chest pain, fainting, sustained palpitations, disproportionate breathlessness or rapidly worsening edema needs medical assessment rather than exercise progression.

Supervised programs can adapt around neutropenia, anemia, central lines, neuropathy and musculoskeletal limitations. Trial regimens are research protocols, not personal prescriptions.

Questions for the care team

  • Do I need baseline or interval cardio-oncology assessment?
  • What symptoms should stop a session and trigger review?
  • Can the program combine aerobic and resistance work while accounting for treatment days and recovery?

Sources and identifiers

Funding and conflicts: Reported funding and conflicts should be checked in each full report; they were not completely verified from the abstracts used here.

Source access and dates: Primary abstracts and the recent review abstract were appraised; full-text funding and adverse-event tables were not completely verified. Sources checked November 5, 2026. Last literature search November 5, 2026.

Educational evidence summary, not individualized medical advice. Exercise around cancer treatment should be adapted to symptoms, blood counts, bone health, cardiopulmonary status, surgical restrictions and the treating team’s guidance.