RESUMO
OBJECTIVE: This study aimed to investigate the relationship between hormone replacement therapy (HRT) types and breast cancer (BC) incidence in postmenopausal women in Korea. METHODS: The nested case-control study used data from the National Health Insurance Service database. Among the women aged ≥50 years who menopaused between 2004 and 2007, BC incidence up to 2017 was analyzed in 36,446 women using or having used HRT for >1 year and in 36,446 women who did not use any HRT for more than 1 year. HRT types and duration were classified into three categories. RESULTS: BC risk (BCR) decreased with tibolone use for all ages. With HRT initiation in women aged ≥50 years, BCR was lower with tibolone and estrogen-progestogen therapy. HRT for <3 years showed lower BCR with tibolone, while higher BCR was observed with estrogen-only therapy. BCR was lower in women of all ages on HRT for >5 years than in the control group. CONCLUSIONS: For women in their 50s, tibolone use lowers BCR; for all ages, the use of any HRT for >5 years showed lower BCR in Korea. These divergent results from western countries could be associated with the specific characteristics of BC in Korea.