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Is Tamoxifen of Value in Preventing Breast Cancer?

Unpublished findings from the U.S. Breast Cancer Prevention Trial (BCPT) announced this spring that tamoxifen may reduce the incidence of breast cancer. However, early results of two European trials raise questions about this conclusion.

An Italian double-blind, placebo-controlled trial enrolled 5,408 women without breast cancer who had had a hysterectomy. (These women were chosen because they would not be at risk for tamoxifen-induced endometrial cancer.) Subjects were randomized to tamoxifen (20 mg/day) or placebo and followed for about four years. So far, the groups have not differed significantly in incidence of breast cancer (tamoxifen, 19 cases; placebo, 22).

A U.K. study randomized 2,494 healthy women with a family history of breast cancer to receive tamoxifen (20 mg/day) or placebo for eight years. At a median follow-up of six years, there was no difference in breast cancer incidence (tamoxifen, 34 cases; placebo, 36; risk ratio, 1.06).

Comment: An editorialist attributes the discrepancy between these findings and those of the BCPT to differences in age (62 percent of the women were under age 50 in the U.K. study, versus 36 percent in the Italian trial and 40 percent in the BCPT study), compliance (poor in the Italian study), and background risk for breast cancer. Noting that yet another large tamoxifen prevention trial is in progress, the editorialist suggests that it would be premature to prescribe tamoxifen widely for prevention until final data are available from the all studies.

— B Jarman

Published in Journal Watch General Medicine July 21, 1998

Citation(s):

Veronesi U et al. Prevention of breast cancer with tamoxifen: Preliminary findings from the Italian randomised trial among hysterectomised women. Lancet 1998 Jul 11 352 93-97.

• Medline abstract (Free)

Powles T et al. Interim analysis of the incidence of breast cancer in the Royal Marsden Hospital tamoxifen randomised chemoprevention trial. Lancet 1998 Jul 11 352 98-101.

• Medline abstract (Free)

Pritchard KI. Is tamoxifen effective in prevention of breast cancer?. Lancet 1998 Jul 11 352 80-81.

• Medline abstract (Free)