By Hope T. Jackson, MD

One of the top cancer groups in the U.S. is urging breast cancer patients to take the drug tamoxifen for 10 years after treatment with surgery, chemo or radiation - effectively doubling the previously recommended five years on the drug.

Tamoxifen targets the hormones estrogen and progesterone, which are important in the development of many breast cancers. The recommendation by the American Society of Clinical Oncology (ASCO) follows two large studies over the last year suggesting that women who take the drug for 10 years may lower their risk of early death and recurrence compared with those who take it for five years.

The women in these studies who took tamoxifen for 10 years cut their risk of dying early by 3 percent, their risk of recurrence by 4 percent, and their risk of cancer in the remaining breast by 12 percent.

Dr. Harold Burstein, co-chair of ASCO's expert panel that wrote the guideline, said the sheer size and duration of the new studies was exactly what was needed to justify this new recommendation.

Burstein added that the new recommendations may be particularly important for younger women who are diagnosed with breast cancer.

"Premenopausal women are not candidates for the other anti-estrogen medications that post-menopausal women are," he said. "Now instead of waiting for them to transition to menopause, which could happen years after their initial five-year tamoxifen course, we can offer uninterrupted continuation of therapy."

ASCO President Dr. Clifford Hudis, who is also chief of breast cancer at Memorial Sloan-Kettering Cancer Center, said the new recommendations underscore tamoxifen's importance in breast cancer treatment.

"Tamoxifen may be more responsible for saving more lives than any other cancer drug," Hudis said. But, he added, "this doesn't mean every woman should take ten full years of therapy. Doctors still need to use judgment and consider the risks and benefits of extended therapy."

Among these risks, according to the guidelines, are a higher chance of endometrial cancer, blood clots, pulmonary embolism and uterine cancer.

Doctor's Take

One of the reasons that this recommendation is so important is tamoxifen is intended to treat the most common type of breast cancer around the world, affecting nearly three out of four women diagnosed with the disease. In other words, if you are a woman who has breast cancer, chances are, it is this type.

What is important to remember, however, is that even in light of this new recommendation, women with breast cancer should still have a detailed conversation with their doctors. Embarking on a decade of treatment is a big commitment, and there are many factors to consider - including the cost of medication and possible side effects.

"While longer duration of anti-estrogen therapy will likely become the norm in the future, it's important to remember that some women will not be appropriate for therapy," Burstein said.