BOSTON--Comments made at the 1996 ASCO annual meeting in support of a limitation on the duration of tamoxifen(Drug information on tamoxifen) (Nolvadex) therapy to 5 years in women with early breast cancer came under fire from several roundtable participants. The overall consensus was that more study is needed before the optimal duration of tamoxifen can be stated with certainty.
The studies discussed at ASCO, a clinical trial conducted by the National Surgical Adjuvant Breast and Bowel Project (NSABP-14) and a small Scottish study, both showed no further benefit of 10 years of tamoxifen over 5 years. These trial results led the National Cancer Institute to publish a clinical alert advising clinicians to limit tamoxifen use to 5 years in women with early breast cancer.
In the NSABP-14 trial, nearly 1,200 premenopausal and postmenopausal women who had been taking tamoxifen for 5 years and had not suffered a relapse were re-randomized to either a second 5 years of the antiestrogen (20 mg/day) or placebo. After 4 years of follow-up, the disease-free survival rate in those assigned to 10 years of tamoxifen was 86%, compared with 92% in those given the drug for only 5 years.
One of the interpretations drawn from these data is that 10 years of tamoxifen therapy is inferior to 5 years, said Nicholas J. Robert, MD, of Georgetown Medical School and Fairfax Hospital, Falls Church, Va. "I think that conclusion may be premature in terms of having data that's still too young to interpret," he said.
In Dr. Robert's view, one of the more disturbing issues raised by NSABP-14 was the apparent lack of protection against contralateral breast cancer afforded by 10 years of tamoxifen, coupled with a slight increase in endometrial cancer.
"So one of the conclusions of the NSABP study is that for node-negative women, giving tamoxifen for more than 5 years did not generate any better outcome for patients," Dr. Robert said.