Aromatase inhibitors and the endometrium

Objective: To investigate the potential impact of aromatase inhibitors, given after stopping tamoxifen treatment, on the endometrium of postmenopausal breast cancer patients. Methods: Review of all available literature of studies on aromatase inhibitor therapy in postmenopausal breast cancer patients previously treated with tamoxifen. Results: (1) Endometrial thickness was found to be significantly lower in patients switched from tamoxifen treatment to aromatase inhibitor therapy, compared to those who continued tamoxifen treatment. This significant difference between the 2 groups was maintained throughout the entire treatment. (2) Vaginal bleeding was significantly more common in patients who continued tamoxifen therapy as compared to those who switched to aromatase inhibitors. (3) Replacement of tamoxifen treatment by aromatase inhibitors in postmenopausal breast cancer patients resulted in the appearance of only few, benign endometrial pathologies. The different endometrial pathologies were more common in patients who continued tamoxifen therapy, compared to patients who switched to aromatase inhibitors. (4) Endometrial cancer was recovered in significantly more patients who continued tamoxifen therapy as compared to those switched to aromatase inhibitors. However, some studies showed no significant statistical differences in the frequency of endometrial cancer diagnosed in the tamoxifen group as compared to the aromatase inhibitor group. Conclusion: These findings may hint on the possibility that aromatase inhibitors may provide a potential protective effect on the endometrium in patients previously treated with tamoxifen.