October 28, 2020

expert reaction to nested case-control studies on HRT and risk of breast cancer

A new study published in The BMJ suggests new estimates of breast cancer risks associated with hormone replacement therapy (HRT) in the UK.

Dr Michael Jones, Senior Staff Scientist in Genetics and Epidemiology at The Institute of Cancer Research, London, said:

“The study in question is very large and uses GP medical records from over 98,000 women with breast cancer, and over 450,000 women without, so the strong statistical associations are unlikely to be due to chance.

“The results of this study generally confirm what has been seen before and is well established – that the use of combined oestrogen plus progestogen HRT is associated with increased risk of breast cancer, and this risk increases with duration of use. But reassuringly, after stopping HRT, the raised risk of breast cancer mostly returns to that seen in non-users of HRT.

“The study also found a small risk associated with oestrogen only HRT use.

“It’s important to note that no one study should be considered in isolation. Even though some risks were found to be slightly smaller than those reported in another meta-analysis of the worldwide epidemiological evidence recently published in 2019, women considering use of HRT should still follow advice given to them by their GPs.”

‘Use of hormone replacement therapy and risk of breast cancer: nested case-control studies using the QResearch and CPRD databases’ by Yana Vinogradova et al. was published in The BMJ at 23:30 UK time on Wednesday 28 October.

DOI: 10.1136/bmj.m3873

Declared interests

Dr Michael Jones: No conflicts of interest to declare, but has previously published in this area.