Does Long-Term Use of Tamoxifen Up Ca Risk?

SAN ANTONIO -- Sharply divergent views regarding the merits of using tamoxifen to reduce breast cancer risk were evident during a breast cancer symposium sponsored by the San Antonio Cancer Institute.

One camp urged caution. They pointed mostly to preclinical data in arguing that tamoxifen's mixed estrogenic and anti-estrogenic effects could spell trouble in the form of an increase in breast cancer with longer-term use.

But clinical trialists countered that there's no hint in the aggregate randomized clinical data to date that would suggest such a problem, even with 10 years of tamoxifen use, compared with 2 or 5 years.

Dr. Victor G. Vogel believes there is persuasive evidence that all U.S. white women aged 35-49 years who have any risk factors for breast cancer would derive substantial net benefit from 5 years of tamoxifen for chemoprevention.

Among white women aged 50-59 at increased risk for breast cancer, however, the decision to employ tamoxifen for chemoprevention needs to be individualized based on whether an intact uterus is present. The National Institutes of Health-sponsored Breast Cancer Prevention Trial demonstrated that the endometrial cancer rate was increased fourfold with tamoxifen chemoprevention therapy among women with an intact uterus in this age group, with much less risk in younger women, explained Dr. Vogel of the University of Pittsburgh.

His conclusions on the net risk-benefit equation for tamoxifen chemoprevention were based on extrapolation from published data on the prevalence of breast cancer risk factors among the U.S. white population as well as results of the major tamoxifen chemoprevention trials.

It's not yet possible to make similar recommendations for nonwhite women. That's because there are no good data on the prevalence of individual breast cancer risk factors--including menarche younger than 12, first birth after age 30, the finding of atypical hyperplasia on breast biopsy, a positive family history, or a BRCAI or BRCA2 mutation--among nonwhites. This shortcoming will be rectified later this year with the release of new National Health and Nutrition Examination Survey (NHANES) data. It will then become possible to perform the same sort of risk-benefit calculations for ...