Public Release: 

Study finds obesity not associated with efficacy of tamoxifen for early-stage breast cancer

Journal of the National Cancer Institute

Obesity is not associated with an increased risk of recurrence among women with early-stage, hormone-responsive breast cancer and does not appear to decrease the effectiveness of the drug tamoxifen, according to a study in the October 1 issue of the Journal of the National Cancer Institute.

Earlier studies had suggested an increased risk of recurrence and death among obese women compared with lean women. However, these studies included women with different stages of breast cancer, note study leader James J. Dignam, Ph.D., of the University of Chicago, and his colleagues. Obesity is associated with a more advanced stage of disease, and this could account for the observed increase in risk of recurrence and death among obese women, the researchers say.

In this study, Dignam and his colleagues looked specifically at women with early-stage, hormone-responsive disease. Their study involved 3,385 women enrolled in a randomized, placebo-controlled study to evaluate the effectiveness of tamoxifen after surgery. The authors examined the association between obesity (defined as having a body mass index of 30.0 kg/m2 or higher) and risks of breast cancer recurrence, of contralateral (opposite) breast tumors, of other new primary cancers, and of overall mortality.

After a median follow-up time of 166 months (13.8 years), obese women had no higher risk of recurrence or deaths attributable to breast cancer than lean women. However, obesity was associated with increased risks of cancer in the contralateral breast, of other primary cancers, and of all-cause mortality. Tamoxifen reduced breast cancer recurrence and mortality to a similar degree, regardless of body mass index.

The authors point out that their study did not consider weight or obesity at different periods of life, including adolescence and early adulthood. And they did not have information about socioeconomic measures, dietary history, and other factors that may have contributed to obesity.

Nevertheless, the findings suggest that obesity does not decrease the effectiveness of tamoxifen for breast cancer recurrence and mortality, the authors conclude, adding that the results support the use of tamoxifen in breast cancer patients of all body types. However, because obesity increases the risk for second cancers and mortality, it may affect the long-term welfare of breast cancer survivors, the authors say.


Contact: John Easton, University of Chicago, 773-702-6241,

Dignam JJ, Wieand K, Johnson KA, Fisher B, Xu L, Mamounas EP. Obesity, tamoxifen use, and outcomes in women with estrogen receptor-positive early-stage breast cancer. J Natl Cancer Inst 2003;95:1467-76.

Note: The Journal of the National Cancer Institute is published by Oxford University Press and is not affiliated with the National Cancer Institute. Attribution to the Journal of the National Cancer Institute is requested in all news coverage.

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