Tamoxifen use limited.

Officials at the National Cancer Institute in Bethesda, Md., last week recommended that doctors treat breast cancer patients with the drug tamoxifen for no more than 5 years. After that period, the drug provides no benefit and may actually cause harm.

The National Surgical Adjuvant Breast and Bowel Project (NSABP), a national network of cancer researchers, initiated the study known as B-14 in 1981 and accrued volunteers until 1988. After tamoxifen showed benefits when used to treat breast cancer patients for 5 years (SN: 2/22/92, p.124), the researchers began giving either a placebo or the drug for an intended period of 5 more years, in order to compare 5 years of treatment to 10 years.

A committee overseeing the study reviewed its data in late October and found that 92 percent of the 575 women who had taken tamoxifen for just 5 years were alive and free of cancer, compared to 86 percent of the women on track to take the drug for 10 years. NSABP stopped the trial early because it found that long-term tamoxifen use fails to save lives and may spur other cancers (SN: 9/25/93, p.207). The findings confirm earlier results from a smaller, Scottish trial.

NCI is sponsoring a controversial NSABP study of tamoxifen as a breast cancer preventive in 16,000 women at high risk of the disease (SN: 5/9/92, p.309). These volunteers are scheduled to take either the drug or a placebo for 5 years. An independent oversight committee for that clinical trial decided that because it limited tamoxifen use to 5 years, the trial should continue; NCI officials concurred. However, the B-14 findings are likely to intensify the debate surrounding the trial (SN: 6/4/94, p.356; 10/22/94, p.268).