RESUMO
BACKGROUND: We aimed to investigate the trends in the incidence and treatment of endometrial cancer (EC) during potentially reproductive age in Japan, with a special focus on the relative oncologic safety of hormonal therapy (HT) over surgery. METHODS: This population-based retrospective cohort study was conducted using data from the Osaka Cancer Registry from 2004 to 2018. Women with EC were first identified and then distributions of age, stage, histology, and initial treatment were examined. Then, the relative oncologic safety of HT over surgery in patients under the age of 50 years was evaluated. RESULTS: Among the 9417 patients with EC, 1937 were diagnosed during their potentially reproductive age (< 50 years). The incidence of EC during potentially reproductive age has increased from 18.5% in 2004-2011 to 21.9% in 2012-2018. ECs during potentially reproductive age more frequently displayed favorable characteristics, such as endometrioid histology, and lower histological grade than those in non-potentially reproductive age. Among the 1223 patients diagnosed with localized endometrioid EC, 74 cases (6.0%) received HT as an initial treatment, while 1100 cases (90.0%) underwent surgery as their initial treatment. When the two treatment groups were compared, there was no significant difference in overall survival (p = 0.3713). The estimated 5-year survival rates were 100 and 98.8% in the HT and surgery groups, respectively. CONCLUSION: EC is increasingly diagnosed during potentially reproductive age in Japan. The use of HT as an initial treatment is increasing, and achieved comparable survival outcomes to urgery against localized endometrioid EC during the potentially reproductive age.