Common breast cancer treatment limits effectiveness of popular weight loss drugs like Ozempic

CHICAGO — A commonly used breast cancer treatment may reduce the effectiveness of weight loss medications. According to a new study, researchers found weight loss interventions are less successful among breast cancer survivors taking aromatase inhibitors compared to women without breast cancer who are not using these treatments.

Aromatase inhibitors are prescribed to treat specific types of breast cancer or as a preventive measure for high-risk individuals. They work by blocking an enzyme called aromatase, which the body uses to produce estrogen. By inhibiting aromatase, the medications reduce estrogen levels in the body, thereby inhibiting the growth of estrogen-dependent cancer cells.

“Our results highlight the need to develop better approaches to manage weight gain in patients with a history of breast cancer taking aromatase inhibitors. Preventing weight gain in this group or treating obesity effectively will improve breast cancer outcomes, prevent further health complications, and improve quality of life for these people,” says lead researcher Sima Fansa, M.D., of the Mayo Clinic in Rochester, Minn., in a media release.

Weight gain and obesity are associated with breast cancer recurrence, breast cancer-related death, and increased risk of heart disease and related complications.

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The study included 99 participants, with 63 women who had a history of breast cancer and were taking aromatase inhibitors and weight loss medications (liraglutide, semaglutide, or phentermine). The remaining 36 women did not have a history of breast cancer and were only taking weight loss medications.

The results demonstrated that women in the breast cancer group experienced less weight loss at the three, six, and 12-month checkpoints compared to women without a history of breast cancer. The difference in weight loss percentages was noticeable (3.7% vs. 5.6% at 3 months, 3.9% vs. 9.5% at 6 months, and 5.2% vs. 10.5% at 12 months).

Semaglutide Rx medical pills in plastic Bottle
Semaglutide Rx medical pills in plastic Bottle (Credit: Shutterstock)

Fansa suggested that the anti-estrogen effect of aromatase inhibitors might explain this difference. These medications can lead to decreased muscle mass, increased fat mass, and changes in energy expenditure, all of which can impact the body’s response to weight loss interventions, including weight loss medications.

The findings underscore the importance of developing improved strategies to manage weight gain in breast cancer patients taking aromatase inhibitors. By preventing weight gain and effectively addressing obesity, better outcomes can be achieved in breast cancer treatment, reducing the risk of complications and enhancing the quality of life for these individuals.

Researchers presented their findings at the Endocrine Society’s annual meeting in Chicago.

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