Risk of endometrial cancer after tamoxifen treatment

A total of 18 studies have been published concerning the possible relationship of tamoxifen to endometrial cancer. Findings range from a protective effect (RR = 0.47) to a risk ratio as high as 15.2. Most studies are based on previous clinical trials of the drug. There are several recurring biases throughout almost all of the studies reported to date. This paper provides a critical review of each of the studies, including identification of bias sources and potential confounding variables. A causal association has not been proven (nor even strongly indicated) for tamoxifen and endometrial cancer, and further investigation, with less bias, will be required to resolve the question.