Tamoxifen's benefit greatest for preventing hormone-dependent breast cancer

January 14, 2003

Tamoxifen reduces the risk of developing breast cancer, but its benefits appear to be limited to women at high risk of the hormone-dependent form of the disease, according to an updated analysis of data from a major trial of tamoxifen. The findings appear in the January 15 issue of the Journal of the National Cancer Institute.

Tamoxifen is a selective estrogen receptor modulator that has been shown in prevention trials to reduce the incidence of estrogen receptor-positive (ER+) breast cancers. However, use of tamoxifen has also been associated with an increase in risk of endometrial cancer and blood clots in the lungs. Because of these risks, the drug is not recommended as a preventive agent for the general population.

Several major trials have attempted to identify a subgroup of high-risk, healthy women that would benefit from tamoxifen. In the Italian Randomized Trial of Tamoxifen, 5,408 women who had undergone a hysterectomy were randomly assigned to receive either tamoxifen or a placebo. An earlier published analysis of the results showed no statistically significant difference in breast cancer incidence between the group receiving tamoxifen and the group receiving a placebo.

In the current update of that data with a median follow-up of 81.2 months, Umberto Veronesi, M.D., and Peter Boyle, Ph.D., of the European Institute of Oncology in Milan, and their colleagues of the Italian Tamoxifen Study Group found that tamoxifen reduced the risk of breast cancer by 82% in women at high risk for ER+ breast cancer. In contrast, tamoxifen use had no significant effect among women at low risk for the disease. Factors that have been suggested to predispose a woman to the ER+ form of the disease include having at least one functioning ovary, having begun menstruation at or before age 13, not having had children before age 24, and being taller than 160 cm (about 5 feet 3 inches).

In addition, among women who had used hormone replacement therapy (HRT) and were in the high-risk group, there was a statistically significant difference in favor of tamoxifen.

The authors note if these findings can be confirmed, it may be possible to limit tamoxifen use for breast cancer prevention to women who are most likely to benefit from the drug.

In an accompanying editorial, Victor G. Vogel, M.D., and Shelly Lo, M.D., of the University of Pittsburgh School of Medicine, say that this updated analysis confirms tamoxifen's role in breast cancer chemoprevention. "What remains unknown is whether this demonstrated reduction in the incidence of breast cancer will ultimately lead to an increased survival or overall health benefit for women at risk, or whether women previously taking HRT should consider tamoxifen for chemoprevention," they write.

They point out that newer agents being evaluated for breast cancer reduction, such as raloxifene and aromatase inhibitors, may be effective without increasing the risk of uterine cancer. "Continued follow-up of the patients in these trials will help to answer these questions in the near future," they conclude.
Contact: Donata Francese, the European Institute of Oncology, 39-027-200-7047, dfrancese@consulenti-associati.it or Lucia Racca 39-025-748-9224, lucia.racca@ieo.it.

Editorial: Clare Collins, University of Pittsburgh School of Medicine, 412-624-2607; fax: 412-624-3184, collcx@msx.upmc.edu

Veronesi U, Maisonneuve P, Rotmensz N, Costa A, Sacchini V, Travaglini R, et al. Italian randomized trial among women with hysterectomy: Tamoxifen and hormone-dependent breast cancer in high-risk women. J Natl Cancer Inst 2003;95:160-5.

Editorial: Vogel V, Lo S. Preventing hormone-dependent breast cancer in high-risk women. J Natl Cancer Inst 2003;95:91-3.

Note: The Journal of the National Cancer Institute is published by Oxford University Press and is not affiliated with the National Cancer Institute. Attribution to the Journal of the National Cancer Institute is requested in all news coverage.

Journal of the National Cancer Institute

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