Study: Drug cuts breast cancer rate for women at risk

April 5, 1998
Web posted at: 7:16 p.m. EDT (2316 GMT)

PHILADELPHIA (CNN) -- Women at increased risk for developing breast cancer may be able to cut that risk nearly in half by taking tamoxifen, a drug now used to treat the disease, according to results of a study by the National Cancer Institute.

The results, reported Sunday in The Philadelphia Inquirer, could potentially affect millions of woman as they age, because women older than 60 are considered at increased risk for developing breast cancer.

Also considered at risk are women with a family history of breast cancer and those with precancerous tissue in their breasts.

Tamoxifen works by interfering with the interaction of breast cancer cells and estrogen, a hormone involved in the division and growth of cancerous cells.

Women at risk for breast cancer: Family history Advanced age Precancerous breast tissue Source: American Cancer Society

"(Tamoxifen) attaches to the receptor in the cells that 'sees' estrogen and prevents the cell from 'seeing' estrogen. So it can actually stop the growth of breast cells and of breast cancer cells," said Dr. Larry Norton of Memorial Sloan Kettering Cancer Center in New York.

Uterine cancer, blood clots are side effects

However, tamoxifen does have potential side effects, including an increased risk of uterine cancer and blood clots traveling from the legs to the lungs. A key question for researchers, and women taking tamoxifen, will be whether those risks are worth the benefit.

Breast cancer statistics: It is estimated there will be 180,300 new cases diagnosed this year There will be an estimated 43,900 deaths from breast cancer this year Source: American Cancer Society

"Blood clots traveling from the legs to the lungs (are) extremely unusual," says Norton. "Cancer of the uterus is slightly increased by the use of tamoxifen, but the effect is very slight. And most people with cancer of the uterus can be cured with hysterectomy, whereas breast cancer is a serious consequence with perhaps life-threatening implications."

But some women's health advocates are urging caution.

"If this turns out to be a good risk-benefit ratio for some women, that will be good news," said Cindy Pearson, executive director of the National Women's Health Network. "(But it is) imperative for researchers to tell women what ... they know about the cost of this benefit. Did any women die of anything caused by tamoxifen?"

Study involved 13,000 women

Risks linked to tamoxifen: Cancer in uterus Blood clots in the lungs Source: American Cancer Society

The cancer institute's study involved 13,000 women in the United States and Canada, making it one of the largest cancer prevention studies ever. Some women were given tamoxifen, others placebos.

For those given tamoxifen over a five-year period, one in 236 developed breast cancer. The expected breast cancer rate was one in 130 women.

The Inquirer reported that the institute recently mailed letters announcing the findings to all of the participants. The results were so promising that women who were given placebos are being offered tamoxifen. All of the study participants will be monitored for the next two years.

The results of the study are scheduled to be formally released Monday. The researchers refused to discuss the results until then.

Medical Correspondent Dr. Steve Salvatore contributed to this report.

Extended coverage:

• In-Depth Health: Cancer
• In-Depth Health: Breast Cancer
• In-Depth Health: Women's Health

Related stories:

• New evidence links breast cancer to electromagnetic fields - March 24, 1998
• Study: U.S. cancer rates declining - March 13, 1998
• New test may help predict recurrence of breast cancer - December 31, 1997
• Chemotherapy, tamoxifen improve breast cancer survival - November 18, 1997
• A call to arms in the fight against breast cancer - November 1, 1997
• Breast cancer studies find radiation reduces deaths - October 1, 1997
• Study: Breast self-exams don't reduce cancer deaths - March 4, 1997
• Tall women higher risk for breast cancer - June 20, 1996

Related sites:

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• Philadelphia Online - The Inquirer and The Daily News
  • Health Philadelphia
  • Women's History Month: Breast Cancer
• National Cancer Institute (NCI)
  • NCI's CancerNet Cancer Information
    • Questions and Answers About Tamoxifen
• Zeneca Pharmaceuticals
• American Cancer Society
• BreastCancerInfo.Com
  • Tamoxifen

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