Association Between Menopausal Hormone Therapy and the Risk of Urologic Cancer: A National Population-Based Retrospective Cohort Study in Korea.

BACKGROUND: This study aimed to evaluate the relationship between menopausal hormone therapy (MHT) and the risk of urologic cancer in women using the Health Insurance Database in Korea. METHOD: We collected Health insurance data from the Health Insurance Review and Assessment Service in Korea between January 1, 2002 and December 31, 2019. Postmenopausal women aged > 40 years were grouped based on MHT exposure status, forming an exposed (MHT users) and an unexposed (non-users) cohort. Types of MHT included tibolone, combined oestrogen plus progestin by the manufacturer (CEPM) or physician (CEPP), and oral and topical oestrogen. Patient characteristics, including age, body mass index (BMI), Charlson comorbidity index, socioeconomic status, residency region, smoking status, alcohol history, physical exercise pattern, reproductive factors such as age at menarche and at menopause, parity, and the period from menopause to inclusion in the study, were reviewed. We performed a Cox proportional hazard analysis to clarify the risk of urologic cancer associated with MHT. RESULTS: Among 2,506,271 participants who had a national health check, 557,031 did not receive MHT and 204,130 received MHT. The median age and BMI of patients were 56 (52-62) and 23.8 (21.9-25.9) kg/m², respectively. According to MHT types, 104,089 patients were treated with tibolone, 65,597 with CEPM, 29,357 with oral oestrogen, 3,913 with CEPP, and 1,174 with topical oestrogen. Among women on MHT, the incidence of kidney cancer was significantly associated with oral (hazard ratio [HR], 1.36; 95% confidence interval [CI], 1.062-1.735) and topical oestrogen (HR, 2.84; 95% CI, 1.270-6.344); other formulations were not associated with kidney cancer. Meanwhile, tibolone was significantly associated with a decreased incidence of bladder cancer (HR, 0.69; 95% CI, 0.548-0.858); other formulations were not associated with bladder cancer. CONCLUSION: MHT in postmenopausal women is significantly associated with the incidence of kidney and bladder cancers.