New Estimates of Breast Cancer Risks Associated with HRT
Results add to existing knowledge and should help doctors and women make the best treatment choices
Oct. 28, 2020 (Science Daily) — A new study provides new estimates of the increased risks of breast cancer associated with use of different hormone replacement therapy (HRT) preparations.
It confirms that HRT use is associated with increased risks of breast cancer, particularly for older women. However, it suggests that, for longer term HRT use, the increased risks are lower than those reported in a recent meta-analysis that combined the results of 24 studies.
Today’s study also shows a more noticeable decline in risks once HRT has stopped, compared with the same meta-analysis.
HRT is used to relieve menopausal symptoms such as hot flushes and night sweats. Treatments include tablets containing estrogen only, or a combination of estrogen and progestogen, as well as patches, gels and creams.
Previous research has shown that long term use of HRT tablets are associated with increased risks of breast cancer, mostly due to progestogens.
Last year, a large meta-analysis reported higher than expected breast cancer risks associated with HRT, but there is still uncertainty around the risks associated with different types and durations of HRT.
So researchers at the Universities of Nottingham and Oxford set out to assess the differences in risks of breast cancer associated with the individual component hormones used in HRT.
They used two UK primary care databases (QResearch and CPRD) linked to hospital records to compare HRT prescriptions for 98,611 women aged 50-79 who were diagnosed with breast cancer between 1998 and 2018 with those of 457,498 women of the same age and from the same general practice who didn’t develop breast cancer.
They analysed risks by HRT type (estrogen only and combined estrogen and progestogen therapy), by recent (1-5 years) and past (5 or more years) use, and by short term (less than 5 years) and long term (5 years or more) use.
Other relevant factors, such as smoking, alcohol consumption, pre-existing conditions (comorbidities), family history, and other prescribed drugs were taken into account.
Overall, 33,703 (34%) women with a diagnosis of breast cancer and 134,391 (31%) controls had used HRT recently or in the past.
- Yana Vinogradova, Carol Coupland, Julia Hippisley-Cox. Use of hormone replacement therapy and risk of breast cancer: nested case-control studies using the QResearch and CPRD databases. BMJ, 2020; m3873 DOI: 10.1136/bmj.m3873