FAQ 14

Does taking Hormone Replacement Therapy (HRT) increase my risk of breast cancer?

The risk of breast cancer is increased in women who take HRT for several years:

  • Combined HRT has been associated with the highest risk
  • For oestrogen-only HRT, risk is lower than with combined HRT. Some studies have not shown an increased risk for oestrogen-only HRT
  • Risk increases with duration of use and returns to baseline within a few years of stopping treatment.

HRT, especially combined therapy, may increase mammographic density, which may adversely affect radiological detection of breast cancer. In the Women's Health Initiative trial, conjugated equine oestrogens (CEE) and CEE plus medroxyprogesterone increased the likelihood of having an abnormal mammogram that needed further evaluation.

(From MHRA Drug Safety Update Bulletin Vol 1, Issue 2, September 2007)

For further details of how HRT can affect breast screening, see the Million Women Study.

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