Tamoxifen Protects Certain Women at High Risk for Breast Cancer

Those who've undergone ovarian removal are shielded from estrogen-linked disease, study finds

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HealthDay Reporter

WEDNESDAY, May 2, 2007 (HealthDay News) -- Tamoxifen helps prevent breast cancer in women at high risk for the disease who have also had their ovaries removed as part of a hysterectomy, researchers report.

The new study, "reaffirms that tamoxifen is still a tremendous drug for prevention of breast cancer in women who are at a high risk for development of the disease," said Dr. Jay Brooks, chairman of hematology/oncology at Ochsner Health System in Baton Rouge, La. He was not involved in the trial.

The study -- an extended follow-up of the Italian Randomized Tamoxifen Trial -- is published in the May 2 issue of the Journal of the National Cancer Institute.

The initial findings of the trial found tamoxifen offered no reduction in women's risk for breast cancer. Nor had some other European trials, some of which looked at women with different risk profiles.

But an earlier and much larger study, the National Surgical Adjuvant Breast and Bowel Project (NSABP) Breast Cancer Prevention Trial, had shown that tamoxifen could cut the risk of estrogen-receptor-positive breast cancer -- tumors that grow in the presence of estrogen. In fact, that trial was halted early, because the risk reduction in invasive breast cancer was so striking.

Here, the authors presented 11-year follow-up data on more than 5,400 women who had undergone a hysterectomy (including having both ovaries removed) and who had been randomly assigned to receive tamoxifen or a placebo for five years.

Ovaries make estrogen, so removing them ensures that no extra estrogen -- which can fuel some breast cancer tumors -- is being produced.

For women at low risk for breast cancer, disease rates were similar whether or not they took tamoxifen, the researchers reported.

The situation was different for higher-risk women. In that case, women taking tamoxifen had lower rates of hormone-receptor-positive breast cancer than those taking a placebo: 1.5 per 1,000 women-years in the tamoxifen group versus 6.26 per 1,000 women-years in the placebo group.

There was also a greater reduction in risk for tumors that were both progesterone- and estrogen-receptor positive, than for tumors which were estrogen-receptor positive and progesterone-receptor negative.

Women in the tamoxifen group also had more side effects, including hot flashes and heart problems. These are noted side effects of the drug. A woman's cardiac risk needs to be assessed before she is started on tamoxifen, the authors stated.

The new study "reaffirms the pioneering work that the NSABP did back in the '90s," Brooks said. "Tamoxifen is still an excellent drug for prevention of breast cancer and is underutilized," he added.

Another expert said newer drugs can help, too.

"Tamoxifen does decrease the risk of invasive breast cancer," said Dr. Alison Estabrook, chief of breast surgery at St. Luke's-Roosevelt Hospital in New York City. "We're hoping that the new aromatase inhibitors which are being tried now for prevention will reduce the risk of breast cancer, which they should."

Aromatase inhibitors, which lower the amount of estrogen in the body by blocking a key enzyme, have far fewer side effects than tamoxifen. Another drug, raloxifene, also has fewer side effects but does not prevent noninvasive breast cancer, whereas tamoxifen works on both, Brooks said.

In other findings, reported in the same issue of the journal, a team at Baylor College of Medicine in Houston used a three-drug combo to block the growth of aggressive breast cancers in mice.

The team added two cancer drugs, gefitinib and pertuzumab, to Herceptin (trastuzumab) to help slow the growth of tumors with higher levels of a protein called HER-2. Herceptin was designed to block HER-2 but proved much more effective with the addition of the other two agents, the researchers found.

A clinical trial will begin soon, said co-investigator Dr. Kent Osborne, director of the Breast Center and Dan L. Duncan Cancer Center at Baylor. "We are very excited to see if our laboratory results can be translated to patients with the more aggressive types of breast cancer," he said in a statement.

More information

There's more on tamoxifen at the U.S. National Cancer Institute.

SOURCES: Alison Estabrook, M.D., chief, breast surgery, St. Luke's-Roosevelt Hospital, New York City; Jay Brooks, M.D., chairman, hematology/oncology, Ochsner Health System, Baton Rouge, La; May 2, 2007, Journal of the National Cancer Institute; May 1, 2007, news release, Baylor College of Medicine

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