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Breast Cancer Health Center

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Obesity Doesn't Hamper Tamoxifen Therapy

Being Obese Won't Decrease Effectiveness of Breast Cancer Treatment Drug
WebMD Health News

Sept. 30, 2003 -- Obesity alone shouldn't lessen the effectiveness of the popular breast cancer treatment drug tamoxifen, but overweight women with breast cancer might face other risks.

Previous studies have suggested that there was an increased risk of breast cancer recurrence and death among obese women compared with lean women. This is because fat tissue produces estrogen, and estrogen plays a role in some breast cancers.

But a new study shows that obesity isn't associated with any higher risk of recurrence of breast cancer among women with early-stage, hormone-responsive breast cancer, nor does it decrease the effectiveness of the breast cancer treatment drug tamoxifen.

Tamoxifen is commonly prescribed to treat or prevent breast cancer recurrence in high-risk women. Breast cancer can respond to estrogen; tamoxifen prevents breast cancer cells from binding to estrogen. It can stop cancer cells from growing and prevent the recurrence of the disease.

Obesity Carries Its Own Risks

Researchers say previous studies on obesity and breast cancer risks included women with different stages of breast cancer, which may have clouded the results because obese women are more likely to have a more advanced stage of breast cancer than lean women.

In this study, researchers looked at 3,385 women with early-stage hormone-responsive disease, a form of breast cancer that depends on estrogen to grow and is responsive to treatment with tamoxifen. Researchers followed the group for an average of about 14 years and then compared the risks of breast cancer recurrence, development of tumors in the opposite breast (known as contralateral tumors), of other new cancers, and of death.

The results appear in the Oct. 1 issue of the Journal of the National Cancer Institute.

The study showed that obese women had no higher risk of cancer recurrence or death due to cancer than lean women. But obese women did have a higher risk of developing other types of cancer or a tumor in the opposite breast and were more likely to die from any cause compared with non-obese women.

Obesity was defined as having a body mass index (BMI, a measure of weight in relation to height) of 30 or higher.

The study also showed that treatment with the breast cancer treatment drug tamoxifen reduced the risk of breast cancer recurrence or death due to breast cancer regardless of the women's BMI.

Researcher James J. Dignam, PhD, of the University of Chicago, and colleagues, say the findings support the use of tamoxifen in breast cancer patients of all body types. But they also warn that because obesity increases the risk of second cancers and death from any cause, it may affect the long-term health of breast cancer survivors.

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