Tamoxifen is a
selective estrogen receptor modulator (
SERM) with pro- and anti-estrogenic properties. Currently it is the most widely used agent for first line treatment against
hormone sensitive metastatic
breast cancer and the only approved hormonal agent for adjuvant treatment of organ confined
breast cancer. Furthermore, its uses have been extended for the treatment of intraductal breast
carcinoma patients. In such settings the most worrisome side effect of
tamoxifen is its ability to increase the rates of
uterine cancers. It has been claimed that most of these
cancers are found at an early stage because of vaginal
bleeding. Moreover, it has been shown that for most women transvaginal ultrasound is an ineffective screening method for the early detection of uterine
carcinomas. It is important, however, to notice that long term
tamoxifen treatment can cause metastatic
uterine cancer--not only
carcinomas but also
sarcomas (mainly malignant mixed mesodermal
tumors. It should be noted that, at least for the special population of BRCA mutation carriers, transvaginal ultrasound can increase our ability for the earlier discovery of
ovarian cancer. Thus, we believe that there is still a place for the use of transvaginal ultrasound in special populations. This is specifically for long term
tamoxifen users (more than the usually recommended five years), women with a higher chance of having uterine
carcinomas (namely very high
body weight, strong family history) and women with a high index of suspicion as carriers of a BRCA mutation. Until new second generation
SERMs and
aromatase inhibitors are shown to possess better anti-
cancer abilities than
tamoxifen, this drug will remain in wide use, however, we must not overlook its possible rare side effects.