Is endometrial cancer risk reduced by oral bisphosphonate use?

TO THE EDITOR: We analyzed the results from the study published in Journal of Clinical Oncology by Newcomb et al.1 The topic is interesting and the conclusions, attractive. The authors carefully controlled participants from the Women’s Health Initiative for weight and body mass index but did not assess some anamnestic confounding data of great relevance. In the exclusion section of the study, they declared that women with a history of antiestrogen use were excluded from analyses. However, they did not report data about previous use of other hormonal agents capable of reducing the production and effects of endogenous estrogens. Gonadotropin-releasing hormone analogs, oral contraceptives, and progestins are widely used in clinical practice for contraception and treatment of benign gynecologic diseases, such as endometriosis, polyps, uterine fibromatosis, and menstrual-cycle disorders. All of these treatments can lower the risk of endometrial cancer, mainly in the case of long-term therapy.2-6 Moreover, previous use of statins was not reported in the article, although these drugs have demonstrated preventive effect in endometrial cancer.7,8 Use of these agents is frequent in clinical practice, mainly in postmenopausal women. Therefore, they represent a possible factor that may influence the incidence of endometrial cancer in the population that Newcomb et al studied. Although recent data9 have confirmed the result from the study by Newcomb et al,1 we believe that the protective use of bisphosphonates for the prevention of endometrial cancer is suggestive but still not conclusive.