First IBIS results show tamoxifen reduces incidence in healthy, high-risk women.(Brief Article)

2002 APR 11 - (NewsRx.com & NewsRx.net) -- First results from the long-awaited IBIS trial into the use of tamoxifen to prevent breast cancer in healthy women at high risk have firmly established that the drug can indeed cut the incidence of the disease.

These preliminary results were presented at the 3rd European Breast Cancer Conference in Barcelona together with an overview of the four breast cancer prevention trials. Results from the previous studies have been mixed.

In addition, nine trials using tamoxifen for treatment of breast cancer patients and who were therefore at high risk of developing a second cancer in the opposite breast, were also reviewed. IBIS lead investigator Professor Jack Cuzick, who is from Cancer Research U.K., told the conference that the incidence of breast cancer was reduced by a third in the women taking tamoxifen in the IBIS trial, with 68 cases of breast cancer compared with 101 among those taking the placebo. When the results of all the prevention trials were combined the overall reduction was 38%. The trials of the adjuvant treatment of breast cancer in patients showed a slightly greater (46%) reduction in the incidence of second cancers in the opposite breast.

The reduction in incidence of breast cancer in IBIS was found only in estrogen receptor-positive (hormone-positive) breast cancers with no effect on cancers that were estrogen receptor-negative. The benefit was the same whatever the age of the woman, whatever the level of risk and whether or not she was taking hormone replacement therapy.

However, while the benefits of tamoxifen for treating breast cancer patients are indisputable, there is still no conclusive answer as to whether the benefits outweigh the side effects for prevention in healthy women, according to Professor Cuzick. "All along the line, we have kept the volunteers in the trial fully informed of developments. That is why we and the Independent Data Monitoring Committee felt it was right to report these preliminary findings at this point. But, I stress that these results are preliminary and it is essential to continue to follow the participants to see if a particular high-risk group of healthy high-risk women can be identified for whom the benefits of tamoxifen clearly outweigh any risks."

It is also too early, he said, to judge the ultimate effect on breast cancer deaths among the prevention trials in healthy women. In the IBIS trial only four breast cancer deaths have been reported so far - two in the tamoxifen arm and two in the placebo arm. However, the likely potential mortality benefit could be calculated if certain factors were assumed. "For high-risk women, we calculate that deaths from breast cancer within 10 years of diagnosis would be reduced by 18%."

Other key findings from IBIS ...