Relationship between menopausal hormone therapy and colorectal cancer: a cohort study utilizing the health insurance database in South Korea (HISK)-II.

Objective: Many studies have demonstrated that menopausal hormone therapy is associated with a reduced risk for colorectal cancer. This study investigated the relationship between specific hormone therapy regimens and colorectal cancer risk in postmenopausal women in South Korea using national insurance claims data.

Methods: This population-based, retrospective cohort study used insurance data provided by the Health Insurance Review and Assessment Service between 2007 and 2020. The hormone therapy group comprised women ≥40 years of age who underwent hormone therapy for the first time between 2011 and 2014. The control group included women ≥40 years of age who visited medical institutions for menopause-related issues during the same period but did not undergo hormone therapy.

Results: After 1:1 propensity score matching, 153,736 women were grouped into either the hormone therapy or nonhormone therapy groups. The incidence of colorectal cancer was 46 and 53 per 100,000 person-years in the nonhormone therapy and hormone therapy groups, respectively. Hormone therapy was associated with an increased risk for colorectal cancer (hazard ratio 1.124 [95% confidence interval 1.002-1.261]). Subgroup analysis, according to hormone therapy type, revealed no significant differences in the risk of colorectal cancer for estrogen plus progestogen or estrogen therapy alone; however, tibolone was associated with an increased risk of colorectal cancer compared to nonhormone therapy (hazard ratio, 1.178 [95% confidence interval, 1.021-1.359]).

Conclusions: This study found an increased risk of colorectal cancer in women receiving hormone therapy, and tibolone was significantly associated with an increased risk of colorectal cancer. However, the magnitude of the increase was small and unlikely to be of clinical significance.