Yes, in many cases, and nothing in the published evidence rules it out. In 1,022 breast cancer survivors at one cancer center, those on semaglutide or tirzepatide had a median weight change of −2.6% at twelve months [2]. A 2026 review by two National Cancer Institute researchers calls the literature limited and largely retrospective [1].
That review also names the people for whom the answer needs care. It is a different question from whether these drugs change the chance of getting cancer, which the cancer-risk evidence covers.
Where the caution comes from
In cancer care, unintended weight loss is a symptom to investigate. It is not an outcome to celebrate.
The review asks providers to weigh the potential negative impact of these drugs in three groups [1]. People with cancer cachexia are one. People with sarcopenic obesity are another. The third is anyone on anticancer treatment that already causes weight loss.
The review adds one more line. In people of normal weight, use for reasons other than type 2 diabetes should start with caution.
The mechanism is the reason. A drug that suppresses appetite can hide or deepen weight loss that has a cause nobody wants. Muscle is the part most at stake, as the lean-mass share of GLP-1 weight loss shows.
What the survivor cohorts found
The breast cancer cohort covered stage 1 to 3 disease, and 79% of patients had type 2 diabetes [2]. Weight loss was modest. Endocrine therapy tracked with weight gain and metformin with loss.
Disease-free survival did not differ between users and matched nonusers. Overall survival did, at a hazard ratio of 0.37.
A second cohort matched 19,608 women with breast cancer and type 2 diabetes into each group [3]. Major cardiovascular events ran 10.6% on a GLP-1 against 13.4% without, a risk ratio of 0.80. All-cause death came in at a risk ratio of 0.38.
A third cohort studied heart damage caused by cancer treatment itself [4]. Among 837 matched users on standard heart-failure therapy, one-year death ran at a hazard ratio of 0.57. Heart-failure flares came in at 0.69.
The heart question may matter more than the weight
Some cancer treatments damage the heart. The review lists that cardiotoxicity as one place GLP-1 drugs might help survivors [1].
The cardiac dysfunction cohort points the same way. It is still one retrospective study with a year of follow-up.
What to do with this
Raise a GLP-1 with the oncology team first. Stage, current treatment and recent weight change all change the answer.
A telehealth intake is built around eligibility for weight loss. It is not built to ask whether chemotherapy ended last year.
The evidence base here is thin, much like GLP-1 use after a kidney transplant. Where treatment goes ahead, protecting muscle is part of it, which the muscle-loss evidence covers.