A new analysis shows that tamoxifen is as effective for black women as it is for white women in reducing the occurrence of "contralateral" breast cancer -- cancer that develops in the healthy breast after cancer in the opposite breast has been treated. In addition, the drug does not cause more side effects in black women, as some had originally feared.
"Regardless of race, tamoxifen can be an appropriate drug for many women," said the National Cancer Institute's Worta McCaskill-Stevens, M.D., who presented the analysis at the American Society of Clinical Oncology meeting in New Orleans. McCaskill-Stevens adds that black women at increased risk for breast cancer can also benefit from tamoxifen as a preventive drug. This finding may help boost recruitment of black women into the Study of Tamoxifen and Raloxifene or STAR, a breast cancer prevention study which is comparing those two drugs in women at high risk of the disease.
McCaskill-Stevens and colleagues at the National Surgical Adjuvant Breast and Bowel Project (NSABP) examined data gathered in nine studies of adjuvant tamoxifen for breast cancer that began in the mid-1980s. These NSABP trials, which involved 15,000 women, successfully established tamoxifen as adjuvant treatment for breast cancer. The same studies later attracted interest in tamoxifen as a possible preventive drug when researchers observed that rates of contralateral breast cancer were lower in the women who took tamoxifen. (Women who have had cancer in one breast are generally at higher risk for developing cancer in the other breast.)
However, none of the studies alone had a large enough black population to conclusively answer whether tamoxifen had the same benefit for white and black women. In the general population, 8 percent of new breast cancer cases occur in black women. By pooling data from all nine NSABP studies, a determination could be made about how beneficial the drug is to black women.
The pooled data included 15,106 women: 1,212 (8 percent) were black and 12,932
(86 percent) were white. Tamoxifen reduced the occurrence of contralateral breast cancer about the same amount in each group, by 43 percent in black women and by 39 percent in white women.
In addition, after controlling for a variety of factors, the rates of endometrial cancer and blood vessel clots – the two main side effects of tamoxifen – increased by about the same amount in both black and white women. (These side effects are relatively rare: Less than 2 percent of women in each group were diagnosed with endometrial cancer and less than
5 percent reported blood clotting.) All women should consider their personal medical history and consult with their physician before taking tamoxifen.
The study was Abstract #269 at the American Society for Clinical Oncology 2000 annual meeting in New Orleans.