Hormone replacement therapy poses increased breast cancer hazard

A recent study has reported a link between hormone replacement therapy (HRT) use and elevated risk of breast cancer, with the risk increasing proportionally with duration of HRT exposure and varying according to body weight and breast density.

The study used data from the Korean National Health Insurance Service database comprising 4,558,376 postmenopausal women who underwent breast cancer screening and regular health check-ups. A total of 696,084 women (15.3 percent) reported current or previous HRT use, among whom 410,304 were exposed to HRT for <2 years, 158,514 for 2 to <5 years, and 127,266 for ≥5 years.

Women who had never used HRT were more likely to have a history of breastfeeding, a fatty breast, no personal history of benign breast diseases, higher body mass index, and comorbidities such as diabetes, hypertension, and dyslipidaemia. Moreover, those who were nonsmokers and did not drink alcohol were less likely to use HRT.

Over a median follow-up of 5.35 years, 26,797 women (0.6 percent) developed breast cancer. Cox analysis revealed that compared with nonusers, HRT users had a 25-percent higher risk of breast cancer (hazard ratio [HR], 1.25, 95 percent confidence interval [CI], 1.22–1.29).

The risk increase was commensurate with HRT duration (<2 years: adjusted HR, 1.08, 95 percent CI, 1.04–1.12; 2 to <5 years: adjusted HR, 1.33, 95 percent CI, 1.25–1.40; ≥5 years: adjusted HR, 1.72, 95 percent CI, 1.63–1.82).

Furthermore, the effects of HRT on breast cancer risk applied to both invasive and in situ cancer and were greater in women who were leaner and those with dense breasts.

The findings suggest that risk stratification would be useful when deciding whether to apply HRT for relief of menopausal symptoms, researchers said.