Tamoxifen breast cancer prevention trial continues

May 12, 1998

LONDON (Reuters) -- An international trial to determine if the drug tamoxifen can prevent breast cancer will continue despite the early closure of a similar study in the United States, British doctors said Wednesday.

The U.S. National Cancer Institute (NCI) cut short its research in April after early results showed tamoxifen reduced the incidence of the disease by 45 percent in high-risk women. NCI decided to allow participants in the study who had been given dummy pills to take the drug instead.

British doctors coordinating the International Breast Cancer Intervention Study (IBIS) in the United Kingdom, Finland, Switzerland and Australia decided not to halt their project because there were still major questions to be answered.

"An enormous amount of effort has been put into this trial, and we owe it to the women participating in this study to ensure that we get clear answers about the risks and benefits associated with the use of tamoxifen for prevention," Dr. Jack Cuzick, the chairman of the IBIS working group, said in a statement.

The British experts had accused their U.S. counterparts of jumping the gun by cutting short the project and releasing their data more than a year early.

They said more information was needed about how long the drug was effective, its impact on survival, which women were most likely to benefit and how hormone replacement therapy (HRT) would interact with the drug.

"Tamoxifen has been shown to be effective in preventing recurrence of breast cancer, so we're very hopeful that it will also be good at stopping the disease occurring in the first place," said professor Tony Howell of the Christie Hospital in Manchester, England.

All 4,000 participants in the IBIS study of women with a family history of the disease had been informed of the U.S. decision, the experts added. Full results of the research are expected to be published in the year 2000.