Contrary to the belief that the breast cancer drug Tamoxifen Effective in Obese and Lean Women (dateline January 3, 2004) | Breast Health News | Imaginis - The Women's Health & Wellness Resource Network

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Tamoxifen Effective in Obese and Lean Women (dateline January 3, 2004)

Contrary to the belief that the breast cancer drug tamoxifen may not be as effective in obese women, a new study finds that the drug works equally well in obese and lean women. The research shows that tamoxifen reduces the risk of a recurrence of breast cancer as well as death from the disease in early-stage breast cancer patients of all weights. However, there were some negative effects of obesity seen in the study, including a higher risk of developing cancer in the opposite breast as well as in other areas of the body. Women who are overweight or obese are encouraged to lose weight to enjoy a variety of health benefits.

Tamoxifen is used to treat breast cancer and prevent the disease in women at high risk. Several studies have found that tamoxifen is effective at reducing tumor size, preventing a recurrence of breast cancer, and increasing patient survival time. Tamoxifen is an "anti-estrogen" and works by preventing estrogen from reaching breast cancer cells. Many breast cancer cells depend on estrogen in order to survive; therefore, blocking estrogen starves these cells.

To determine whether tamoxifen is as effective in obese breast cancer patients as it is in patients of healthy weights, James J. Dignam, of the Department of Health Studies and Cancer Research Center at the University of Chicago and the National Surgical Adjuvant Breast and Bowel Project (NSABP) of Pittsburgh, Pennsylvania, and colleagues studied 3,385 women who had been diagnosed with early-stage breast cancer. Each of the women received either tamoxifen or a placebo (an inactive pill) after undergoing breast cancer surgery. The researchers investigated the relationship between obesity and breast cancer recurrence, contralateral breast cancer (breast cancer in the opposite breast), and the risk of death from breast cancer.

The study found that obese women who took tamoxifen were no more likely to experience a recurrence of breast cancer or die from the disease after 14 years of follow-up, compared to lean women who took tamoxifen.

However, obese women were 1.5 times more likely to develop breast cancer in the opposite breast, 1.6 times more likely to develop cancer in other areas of the body, and 1.3 times more likely to die of other causes, compared to healthy weight women. Therefore, obesity was associated with negative health effects in the study.

In the study, the researchers labeled women obese, overweight, or normal weight based on their body mass index (BMI). BMI measures a person’s total body fat based on weight and height. It is derived by multiplying a person's weight in pounds by 703 and then dividing it twice by the person’s height in inches. According to federal guidelines:

  • BMI of 24 or under = not overweight
  • BMI of 25 to 29.9 = overweight
  • BMI of 30 or greater = obese

Click here to view a table that calculates BMI based on height and weight. 

The researchers hope their study findings will alleviate fears that tamoxifen may not be as effective in obese women. At the same time, they also hope it will encourage obese women and their physicians to better understand the negative impact of excess weight on health.

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