A simulation study published in JAMA Network Open on November 10, 2026, suggests that chemotherapy for breast cancer may accelerate biological aging and raise survivors’ risk of dying earlier from other conditions, even as treatment can improve the chance of curing cancer.

Researchers at Georgetown University’s Lombardi Comprehensive Cancer Center and colleagues used prior evidence linking chemotherapy to blood levels of p16, a marker of cellular senescence, to model biological aging over survivors’ remaining lifetimes.

The model compared chemotherapy regimens associated with more or less cellular damage and estimated effects on deaths from causes other than breast cancer, not on breast cancer outcomes.

Among women aged 30 to 79, those modeled as receiving the most cytotoxic regimens were projected to lose an average of 9.4 remaining life years because aging-related diseases would begin earlier.

The projected effects may be greatest for women receiving the most intensive chemotherapy, particularly at younger ages; the model did not assess hormone, radiation, immune or targeted therapies.

These figures are projections, not observed outcomes: the researchers did not enroll or follow patients, and the estimates rely on assumptions from earlier studies and a single aging marker whose links to illness and death are not fully established in people.

Public summaries do not identify the regimens behind the estimate, break results down by age or provide an uncertainty range, and the study did not show that chemotherapy causes early death through aging or test ways to prevent the projected effects.

The findings are not a reason to refuse recommended chemotherapy, which can be lifesaving; patients should discuss treatment benefits and risks, as well as whether genomic tests apply to them, with their oncologist.

For survivorship care, patients can ask for a care plan, keep up with recommended heart, metabolic and bone-health checks, and raise new symptoms with their care team; exercise and some medications may help slow accelerated aging, but this study did not test those approaches.

The work was conducted through CISNET, a National Cancer Institute-supported modeling consortium, and the researchers plan to extend the framework to other treatments and incorporate patient-specific factors and additional aging markers.

The authors say their findings should spur research into biological-age testing and more personalized survivorship care, not change treatment decisions that prioritize curing breast cancer.

The research has potential relevance for a large and growing population: female breast cancer survivors are the largest group among America’s 18.6 million cancer survivors, and their number is projected to reach 5.3 million by January 2035, one million more than in 2025.