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Dr. C. Joseph Bennett, Navigating Cancer, 12/11/12

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Tamoxifen for 10 years?

As many of my readers know, over the past several days I have had many questions thrown at me regarding a drug called tamoxifen.

Tamoxifen is one of the most successful cancer drugs ever used in this country. For women with estrogen receptor-positive (ER-positive) breast cancer, it was the first drug widely used to help slow the progression of cancer, and in some cases lower the risk of getting breast cancer. For decades, we have recommended that women take the drug for five years, thinking that the benefit of the drug lasted five years but not beyond, and also concerned about a few possible long-term side effects that can occur with tamoxifen.

But that may all change, because patients with early-stage ER-positive breast cancer seem to show evidence of an improvement in the risk of recurrence and the risk of death if they continue tamoxifen for 10 years instead of just five years. The data from this study, recently presented, was published online Dec. 5 in The Lancet to coincide with a presentation at the annual San Antonio Breast Cancer Symposium.

Researchers from the University of Oxford in the United Kingdom assessed the effect of continuing therapy with tamoxifen for 10 years instead of stopping at five years. A group of 12,894 women from the worldwide “Adjuvant Tamoxifen: Longer against Shorter” trial who had early breast cancer and had completed five years of treatment were randomly allocated to continue treatment to 10 years or stop treatment. The effects on outcome were reported for the 6,846 women with ER-positive disease.

The researchers found that continuation of tamoxifen correlated with significant reductions in the risk of breast cancer recurrence, breast cancer deaths, and the overall risk of death. During years five to 14, the cumulative risk of recurrence was 21.4 percent for women allocated to continue tamoxifen and 25.1 percent for controls, and the breast cancer death rate was 12.2 and 15 percent, respectively. Long-term follow-up is ongoing. So, as you can see, there is a small but real benefit noted with continuing treatment.

These results, taken together with results from previous trials of five years of tamoxifen treatment versus none, suggest that 10 years of tamoxifen treatment can approximately halve breast cancer mortality during the second decade after diagnosis. So, if you are on tamoxifen, talk to your physician, look at all factors regarding this medication, including the side effects and long-term risks, and determine individually whether taking tamoxifen for 10 years is the right thing for you.

Dr. Bennett is a board certified radiation oncologist at the Robert Boissoneault Oncology Institute and a member of the Citrus County Unit of the American Cancer Society. Watch Navigating Cancer, hosted by Dr. Bennett, on WYKE TV, every Tuesday at 7:30 p.m. and every Thursday at 10 a.m. If you have any suggestions for topics, or have any questions, please contact him at the Robert Boissoneault Oncology Institute, 522 North Lecanto Highway, Lecanto, FL 34461, or E-mail at cjbennett@rboi.com. ­