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Tamoxifen Era Ends

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WebMD Health News

Dec. 10, 2001 -- Tamoxifen no longer rules the roost as the leading hormonal treatment for breast cancer.

Reports from this week's San Antonio Breast Cancer Conference show that a newer type of breast-cancer treatment works better than tamoxifen (Nolvadex). The new drugs also appear to avoid tamoxifen's small but important increased risk of uterine cancer.

"Today we have come to the end of the tamoxifen era," Matthew J. Ellis, MD, PhD, tells WebMD. "Now we clearly have tamoxifen replacements that are more effective."

Ellis is clinical director of the breast cancer program at Duke University. He says hormonal therapies have been used to shrink tumors before surgery, to prevent cancer recurrence after surgery and traditional chemotherapy, and to fight advanced breast cancer.

Hormonal treatments for breast cancer work by blocking the tumor-promoting effects of the female sex hormone estrogen. A woman's body keeps on making estrogen even after menopause. Tamoxifen keeps this estrogen from revving up breast cancer cells. The newer drugs, known as aromatase inhibitors or AIs, block the key chemical the body uses to turn other hormones into estrogen. Two of them have received FDA approval: Arimidex and Femara.

One of the most important studies reported at the conference was a huge study of hormonal therapy to prevent breast cancer relapse. This "adjuvant therapy" study enrolled more than 9,000 women from 380 cancer centers in 21 countries. These postmenopausal women -- all of whom had completed first-time surgery and chemotherapy for early breast cancer -- received Arimidex, tamoxifen, or a combination of the two.

After about 31 months of treatment -- with more than 33 months of follow-up -- 10% of the women in the Arimidex group had breast cancer relapse or died. This happened to 12% of the women who got tamoxifen alone or in combination with Arimidex. For women whose tumors were hormone sensitive, Arimidex reduced the risk of relapse by 22%.

"Tamoxifen has been the standard adjuvant therapy for several decades," Lawrence Wickerham, MD, tells WebMD. "Over two-and-a-half years of follow-up, Arimidex shows an advantage."

Wickerham, associate chairman of The National Surgical Adjuvant Breast and Bowel Project (NSABP), was not involved in the study.

"If these data hold up, AIs likely will become an option if not the option for adjuvant treatment of breast cancer," Wickerham says.

A smaller trial suggests that Arimidex may not be the only AI that works better than tamoxifen. Ellis reported a study that compared Femara to tamoxifen in 324 women with inoperable breast cancer. The women received the drugs for four months. Tumor shrinkage -- making surgery possible -- was seen in 60% of women taking Femara and in 41% of women taking tamoxifen.

Ellis warns that this trial is too small to prove Femara works better than tamoxifen. Larger studies are under way.

Ellis pointed to another study suggesting that Femara may be useful in treating advanced metastatic breast cancer.

"That is quite an exciting result," he says. "To see improvement in the metastatic setting is relatively uncommon. The findings suggest that if 100 patients with advanced breast cancer choose Femara treatment over tamoxifen, one year later eight extra women will be alive."

AIs do appear to increase a woman's risk of osteoporosis. Ellis notes that drugs to prevent bone loss can help with this serious side effect.

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