Menopausal hormone therapy may be protective against colorectal cancer

Women exposed to menopausal hormone therapy (MHT), including oestrogen‐only preparations and oestrogen combined progestin therapy, appear to have a lower risk of colorectal adenocarcinoma, a study has found.

The study drew data from the Swedish Prescribed Drug Registry and included 290,186 women who had ever used MHT. Ever-users were defined as receipt of ≥1 dispensed prescription of systemic MHT during 2005–2012 in Sweden. All CRC cases after drug initiation were extracted from the Swedish Cancer Registry.

Multivariable conditional logistic analysis showed that relative to nonuse, MHT use was associated with a lower likelihood of colon (odds ratio [OR], 0.67, 95 percent confidence interval [CI], 0.63–0.72) and rectal adenocarcinoma (OR, 0.66, 95 percent CI, 0.60–0.73), especially among women aged 40–60 years.

Current users of oestrogen‐only preparations, particularly oestradiol and oestriol, were less likely to have colorectal malignancies compared with nonusers (colon: OR, 0.73, 95 percent CI, 0.65–0.82; rectal: OR, 0.76, 95 percent CI, 0.64–0.90). Interestingly, the protective effect of the said preparations was more pronounced for past users (colon: OR, 0.49, 95 percent CI, 0.43–0.56; rectal: OR, 0.36, 95 percent CI, 0.28–0.45).

Meanwhile, current use of oestrogen combined progestin therapy conferred a less prominent risk reduction (colon: OR, 0.62, 95 percent CI, 0.54–0.72; rectal: OR, 0.60, 95 percent CI, 0.49–0.74) relative to past use. Tibolone, however, was associated with an increased risk of left‐sided colorectal adenocarcinoma.

The associations did not differ by MHT administration (ie, oral and cutaneous).