The effect of menopausal hormone therapy on thyroid cancer survivors from the National Health Insurance Database in South Korea cohort.

[OBJECTIVE] There is a lack of research on how menopausal hormone therapy (MHT) affects the prognosis of postmenopausal thyroid cancer (TC) survivors. This study aimed to evaluate the association between MHT and the risk of death in postmenopausal TC survivors.

[METHODS] This retrospective cohort study used the data of women with the diagnostic code for TC from the Korean National Health Insurance Database between 2007 and 2021. The postmenopausal women with TC who received radical treatment such as surgery or/and radioactive iodine therapy were divided into two groups - MHT group and non-MHT group - according to whether or not they received MHT after TC treatment. The risk of death in TC survivors was analysed according to the type and duration of the MHT regimen.

[RESULTS] Among postmenopausal TC survivors, the risk of death did not differ between the women with MHT duration > 5 years and the non-MHT group, with a hazard ratio (HR) of 0.964 [95 % confidence interval (CI) 0.697-1.334] (p = 0.826). However, MHT duration < 5 years was associated with increased risk of death, with the MHT group having an HR of 1.744 (95 % CI 1.105-2.753) (p = 0.017) compared with the non-MHT group. A trend was observed towards increased risk of death in women with MHT duration ≤ 6 months, with an HR of 1.703 (95 % CI 0.98-2.962) (p = 0.059). The risk of death did not differ between women with MHT duration > 6 months and women in the non-MHT group (HR 1.205, 95 % CI 0.79-1.839) (p = 0.064). In analyses by MHT regimen, no increase in the risk of death was observed for any MHT regimen for any duration.

[CONCLUSION] The risk of death in postmenopausal TC survivors who used MHT for > 5 years did not differ from that of their counterparts who did not use MHT. However, postmenopausal TC survivors who used MHT for < 5 years, particularly those who used MHT for < 6 months, had a higher risk of death than their counterparts who did not use MHT.