Real-world practice of estrogen therapy after surgery for endometrial cancer: a descriptive study using a Japanese claims database

Background Estrogen therapy (ET) plays a key role in maintaining the post-surgical quality of life of patients with endome-trial cancer. This study investigated the reality of the use of ET after endometrial cancer surgery in Japan.Methods Using a healthcare database in Japan, patients who underwent surgery for endometrial cancer between the ages of 40 and 59 years from January 2006 to March 2021 were included. The cumulative prescriptions of ET after endometrial cancer surgeries in patients who had received chemotherapy or radiation therapy (adj-group) and those who did not (non-adj-group) was estimated using the Kaplan-Meier method.Results Of the 1475 patients, 115 received ET, among whom transdermal estradiol was initiated in 100 (87.0%) individuals. The cumulative proportions of ET prescription 24 months after surgery [95% confidence intervals (CIs)] were 0.088 [0.072, 0.11] in the non-adj-group and 0.058 [0.040, 0.084] in the adj-group. The cumulative proportion [95% CI] of women who received ET at 24 months after surgeries decreased with increasing age, ranging from 0.29 [0.21, 0.38] in the 40-44 years old to 0.009 [0.002, 0.034] in the 55-59 years old women in the non-adj-group and from 0.17 [0.094, 0.31] in the 40-44 years old to 0 in the 55-59 years old women in the adj-group.Conclusion The present study shows that ET after endometrial cancer surgery may be underused, even in women who underwent surgery between 40 and 44 years of age and without adjuvant therapy.