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After Breast Cancer: How Long on Tamoxifen?

5 Years Is Better than 2 for Younger Patients, Italian Study Shows
WebMD Health News
Reviewed by Louise Chang, MD

Oct. 24, 2005 -- Taking the drug tamoxifen for five years instead of two years improves survival in younger women with breast cancer, according to a new Italian study.

But the survival advantage didn't show up right away and was only seen in women younger than 55 with estrogen receptor-positive cancer. Estrogen receptor-positive cancer grows when exposed to estrogen and is more responsive to antiestrogen therapy.

Tamoxifen, which works as an antiestrogen, has long been a staple of breast cancer treatment. The researchers aren't calling for any treatment changes since their study was relatively small.

The report by Maurizio Belfiglio, MD, and colleagues appears in Cancer.

Belfiglio works in the clinical pharmacology and epidemiology department of the Italian research institute Consorzio Mario Negri Sud.

About Tamoxifen

Some (but not all) breast cancers are fueled by the hormone estrogen. Tamoxifen blocks estrogen from latching onto estrogen receptor-positive breast tumors.

The most common side effects of tamoxifen are hot flashes and vaginal discharge. But there is a higher risk for blood clots, stroke, and uterine cancer, which can be fatal. Women who are pregnant or are planning to become pregnant should not take the medication. Also, people with a history of blood clots or who are already taking blood-thinning medication should not take tamoxifen.

Tamoxifen has been used in breast cancer therapy for more than 20 years. It's usually given for five years after initial breast cancer treatments (such as surgery, chemotherapy, and radiation).

Could a shorter dose of tamoxifen work as well for survival? That question was explored by Belfiglio's team.

Tamoxifen: 2 Years vs. 5 Years

All of the women in their study took tamoxifen for at least two years. About half stopped after two years; the rest took tamoxifen for a total of five years.

The women were 50-70 years old when the study started. Women with early-stage invasive breast cancer were included.

About 60% had estrogen receptor-positive breast cancer. About 25% hadn't had their cancer's estrogen status checked.

Virtually all of the women got surgery for breast cancer. About 40% got radiation and 10% got chemotherapy.

Survival Advantage

A total of 549 women died during the nine-year study. Survival was 44% more likely for younger women (up to age 55) with estrogen receptor-positive breast cancers, the study shows.

The survival benefit of taking tamoxifen for five years instead of two years wasn't immediate. That advantage appeared nine years after the women had first been diagnosed with breast cancer.

Older women had different results.

"No clear benefit was documented in women older than 55 years of age" who took tamoxifen for five years instead of two years, the researchers write.

More Work Ahead

The small number of patients might have mattered, so more studies are needed, the researchers note.

"We believe that our findings should only be used to generate further investigation, rather than to draw definitive conclusions, and to underline the importance of a long follow-up in trials exploring the effects of hormonal therapy in breast [cancer]," they write.

The study was funded by the drug company AstraZeneca Italia.

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