Tamoxifen has been the gold standard for treating the most common type of breast cancer, but now Fred Hutchinson researchers have found that taking the drug long-term may significantly increase the risk of a more aggressive form of breast cancer.
Nothing stops Teresa Gustafson from pounding the pavement.
"I'm a very active person," said Gustafson. "I have three young children, and I'm a P.E. teacher, so I'm extremely busy, extremely active."
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Gustafson is also a breast cancer survivor. She's had four rounds of chemo and two years on Tamoxifen. It's a drug that blocks a tumor's ability to use estrogen, but at a price.
"What we found in the study is that while Tamoxifen lowers the risk of the more common type of breast cancer by about half, it increases the risk of this more aggressive type of second breast cancer by over four-fold - over four times of an increase in risk," said Dr. Christopher Li with Fred Hutchinson Cancer Research Center.
Li was the first to discover this connection in 2001. His newest study is much more extensive. It looked at more than 1,000 women from the Seattle-Puget Sound region who were over 40 years old and diagnosed with the most common kind of breast cancer.
Of these, about? one third went on to develop a second breast cancer in the other breast. Nearly all used Tamoxifen.
"The increase in risk was only among women who used Tamoxifen for five years or longer. Women who used it for less than that period of time did not seem to have an increase in risk," said Li.
Gustafson switched to a newer drug called an aromatase inhibitor, but Li says there is not enough research yet to know if those drugs are as effective in preventing deaths from breast cancer which Tamoxifen clearly does.
Li says there's no reason for doctors to stop prescribing Tamoxifen.? This is just one more potential side effect to be on the lookout for.? Others include blood clots, strokes, uterine cancer and cataracts.
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