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Optimal Duration of Tamoxifen Requires More Investigation

Optimal Duration of Tamoxifen Requires More Investigation

ABSTRACT: An expert panel of nine international cancer researchers and practicing oncolo-gists met in Boston to discuss the past, present, and future uses of antiestrogens in the treatment of breast cancer. This article represents the first in a series of reports based on the symposium presentations that will be featured in subsequent issues of Oncology News International.The symposium was sponsored by Zeneca Pharmaceuticals.

BOSTON--Comments made at the 1996 ASCO annual meeting in support
of a limitation on the duration of 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.

Node-Positive Patients

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