For most women who have been treated for breast cancer, taking tamoxifen (an estrogen blocker in breast tissue) can cut their odds of recurrence but for how long to take the drug to maximize benefit, has not been clear. Now a new study shows 10 years of tamoxifen treatment is better than five, lowering the risk of recurrence by a quarter and the risk of dying by 29 percent.
The randomized, placebo-controlled study of 6,846 women by Dr. Christina Davies of the University of Oxford in England and colleagues was published by the UK medical journal Lancet, and has the potential to change clinical guidelines. The benefits of tamoxifen apply only to women with estrogen-receptor-positive tumors.
Tamoxifen does have the potential to cause endometrial cancer, but the disease is rarely fatal and the extended benefits seem to clearly outweigh the risks, researchers said.
ACSH s Dr. Elizabeth Whelan says this study does pose a dilemma for women who had completed a five-year course of the drug some time ago, and stopped. Should they go back on it? The study doesn t answer that. And of course this study says nothing about the other estrogen-modulating drug, raloxifene which has shown even better tumor-recurrence prevention nor about the aromatase inhibitors.