Breast cancer treatments limit effectiveness of weight loss medications, finds study

Washington [US], June 18 : Breast cancer medicines known as aromatase inhibitors may diminish the benefit of weight loss therapies, according to a new study presented at ENDO 2023, the Endocrine Society's annual meeting in Chicago, Illinois.

The study discovered that weight loss drugs are less successful in breast cancer survivors taking aromatase inhibitors than in women without a history of breast cancer who are not taking aromatase inhibitors.

Aromatase inhibitors are used to treat or prevent the recurrence of certain forms of breast cancer. They may also be used to help prevent breast cancer in some women who are predisposed to it. These drugs inhibit the function of aromatase, an enzyme that the body utilises to produce oestrogen in the ovaries and other tissues. By inhibiting aromatase, the body produces less oestrogen, which may inhibit the growth of cancer cells that require oestrogen to proliferate.

"Weight gain is a common concern in breast cancer survivors," said lead researcher Sima Fansa, M.D., of the Mayo Clinic in Rochester, Minn. She said studies have shown that aromatase inhibitors may be a risk factor for weight gain. Weight gain and obesity, in addition to being associated with breast cancer recurrence and breast cancer-related death, can lead to heart disease and heart-related death.

"This is the first study assessing response to weight loss medications in a subgroup of breast cancer survivors taking aromatase inhibitors," Fansa said. "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."

The study included 99 patients63 women with a history of breast cancer taking aromatase inhibitors and weight loss medications (liraglutide, semaglutide or phentermine); and 36 women without a history of breast cancer who were not taking aromatase inhibitors but were taking weight loss medications.

The women in the breast cancer group lost less weight at 3, 6 and 12 months compared with the women without a history of breast cancer (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).

"We believe that this difference may be explained, at least partially, by the anti-estrogen effect of aromatase inhibitors," Fansa said. "Aromatase inhibitors can lead to decreased muscle mass, increased fat mass, and changes in energy expenditure. This may affect the body's response to weight loss interventions, including weight loss medications."