Hormone replacement therapy (HRT) is commonly prescribed to women to relieve the symptoms of menopause. However, recent studies have shown that the prolonged use of HRT might be associated with an increased risk of breast cancer. This study aims to examine the association between HRT and the risk of breast cancer in women.

This collection of two case-control studies included a total of 98,611 women aged 50-79 with a confirmed primary diagnosis of breast cancer. The participants were matched with 457,498 female controls. The association between breast cancer and HRT was evaluated. The primary outcome of the study was breast cancer diagnosis and the odds ratios for HRT types.

The findings suggested that 33,707 women (34%) with breast cancer and 134,391 controls (31%) used HRT one year before the index date. The long-term and recent use of estrogen-only and combined estrogen-progesterone therapy was associated with an increased risk of breast cancer (HR 1.15). The risk for combined progestogens was the highest for norethisterone (1.88) and the lowest for dydrogesterone (1.24)

The research concluded that the use of estrogen-only, combined estrogen-progesterone, and progesterone-only therapy was associated with a higher risk of breast cancer in women aged 50-79.

Ref: https://www.bmj.com/content/371/bmj.m3873