Obesity May Increase the Risk of Breast Cancer Recurrence

Results of a new study suggest that women with obesity taking an aromatase inhibitor for hormone receptor–positive breast cancer may be at higher risk of experiencing cancer recurrence.

October is breast cancer awareness month, and currently, more than four million women in the United States are undergoing treatment, have just finished treatment for breast cancer, or have a history of the condition.

Women with a history of breast cancer often worry the cancer will return.

A 2022 study found that women at higher risk for late breast cancer recurrence were those with initial tumors larger than two centimeters, lymph nodes positive for cancer, and ER-positive (hormone-receptive) breast cancer. Nevertheless, there are treatments that can help reduce the risks.

For example, to help prevent the risk of breast cancer reoccurrence, healthcare providers can prescribe aromatase inhibitors — an endocrine therapy that helps lower estrogen levels — for women with hormone receptor-positive breast cancer.

Although aromatase inhibitors can reduce the risk of recurrence, scientists aren't sure if they work as well in women with obesity.

To find out more, researchers from Denmark and Sweden analyzed data from 1998 through 2016 of 13,230 postmenopausal women diagnosed with stage I to III HR+ breast cancer. All participants took aromatase inhibitors.

Their findings, published on October 13 in JAMA Network Open, found the risk of breast cancer recurrence among women taking aromatase inhibitors was higher among those with obesity.

To conduct the study, the research team categorized the participants by body mass index (BMI) using WHO guidelines and compared healthy weight participants to those in other weight groups. When first diagnosed, 2.2% of participants were underweight, 44.4% had a healthy weight, 32.5% had overweight, 14.4% had obesity, and 6.5% had severe obesity.

Over an average six-year follow-up, 1,587 participants experienced breast cancer recurrence.

After comparing the different BMI groups, the scientists found that women who were underweight had a similar risk of breast cancer recurrence as participants with a healthy weight.

Though participants who were overweight had a higher risk of recurrence than women with a healthy weight, the results were not statistically significant.

However, women with obesity were 18% more likely to experience breast cancer recurrence than those with a healthy weight. And among women with severe obesity, the risk of recurrence increased to 32%.

The study could not determine whether other treatments like tamoxifen would work better than aromatase inhibitors in women with breast cancer and obesity. So, more research is needed to help answer that question.

Still, the authors say the results of this study underscore the need to personalize treatments for women with breast cancer and higher BMIs. They also suggest future studies should examine whether endocrine therapies other than the currently recommended aromatase inhibitors might be more effective in women with obesity and early-stage HR+ postmenopausal breast cancer.

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