Sustained effect of the aromatase inhibitors anastrozole and letrozole on endometrial thickness in patients with endometrial hyperplasia and endometrial carcinoma

Objective: To investigate whether there may be a role for aromatase inhibitors (AIs) in the treatment of endometrial hyperplasia (EH) and endometrial adenocarcinoma (EA) in postmenopausal women, a retrospective study on the effect of aromatase inhibitors (anastrozole or letrozole) was conducted for 16 patients who were not amenable to surgical treatment. Main outcome measure: Resolution of endometrial thickening measured by transvaginal ultrasound at 3-month intervals; the response of metastases was assessed by standard oncological criteria. Results: In all, 16 patients were studied. The BMI of 13 of the 16 patients was known and ranged from 20.7 to 47.7 (mean 34.5) kg/m(2) During treatment with AIs, mean endometrial thickness in the eight patients with EH decreased progressively by 81.7% from 14.7 mm at the start of treatment to 2.7 mm following 36 months of treatment. A greater original mean endometrial thickness of 17 mm was seen in the four patients with localised EA, this fell progressively by 67.1% to 5.6 mm following 36 months of treatment. No responses were seen in four patients with metastatic disease. Conclusion: Our results indicate that treatment of EH with anastrozole or letrozole can reduce endometrial thickness as seen ultrasonically, and that in some cases AI treatment can reduce endometrial thickness in patients with localised EA. We found no evidence to indicate that AI treatment prevents disease progression in patients with metastatic EA. Further investigations will be necessary to validate our findings from this small retrospective study and to compare AI inhibitor treatment with topical progestogen therapy.