When Fighting One Disease Causes Another

Breast cancer drug tamoxifen increases diabetes risk

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) More and more research is showing a link between breast cancer and diabetes. Yet, only a handful of studies have looked at the relationship between cancer drugs and the risk of diabetes.

Tamoxifen (Nolvadex, Istubal, Valodex) therapy for breast cancer is associated with a higher risk of diabetes in older breast cancer survivors.

"Watch out for diabetes if you have taken tamoxifen."

Lorraine L. Lipscombe, M.D., M.Sc., of the Women's College Research Institute in Toronto, and colleagues suspected the tamoxifen may increase the risk of diabetes because of its impact on estrogen, the main sex hormone in women.

Their findings seem to agree, at least partially, to their hunch. Even though the researchers cannot say how tamoxifen raises the risk of diabetes, they found a strong association between taking the drug and diabetes.

Tamoxifen is an oral drug that interferes with estrogen, which is known to promote the development of breast cancer.

Dr. Lipscombe and colleagues found that women who took tamoxifen were nearly 25 percent more likely to get diabetes, compared to women who did not take the drug.

According to the study's authors, this finding suggests that tamoxifen could worsen some women's odds of developing diabetes, especially among women who are already vulnerable to the disease.

To come to these findings, the researchers identified more than 14,000 women over 65 years of age with early stage breast cancer between April 1, 1996 and March 31, 2006. They compared diabetes risk in tamoxifen users and those who did not take tamoxifen.

They also studied the risk of diabetes in those taking aromatase inhibitors, but found no association between use of that drug and diabetes.

The authors note that more research is needed to get a better understanding of the link between Nolvadex and diabetes.

The results of this nested case-control study are published in the journal Cancer

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Review Date: 
October 10, 2011
Last Updated:
October 11, 2011