Current combined HRT use doubles risk of breast cancer

Current use of hormone replacement therapy (HRT) increases the risk of breast cancer, with the largest increase associated with combined estrogen-progestagen use, according to findings from the British Million Women Study.

The report, in the August 9th issue of The Lancet, suggests that the risk declines significantly after one year of discontinuation and returns to baseline within 5 years.Dr. Valerie Beral, of Cancer Research UK in Oxford, and Million Women Study Collaborators recruited more than one million women aged 50 to 64 between 1996 and 2001. The investigators analyzed the 80% of women who were postmenopausal, with follow-up averaging 2.6 years for analyses of cancer incidence and 4.1 years for analyses of mortality due to breast cancer. About half of the women had used HRT at some time.Overall, the relative risk (RR) for current HRT users compared with never users was 1.66. Among women who had ceased use of HRT in the previous year, the relative risk was only slightly elevated, RR = 1.14. For those currently using estrogen-only preparations, the RR was 1.30; for those using estrogen-progestagen, the RR was 1.88, and among tibolone users it was 1.45.Among those using combination HRT, the RR was 1.70 for those whose treatment was less than 5 years and 2.21 for those using it longer. The greatest documented increase was among those using combined equine estrogen and medroxyprogesterone acetate — the combination used in the Women’s Health Initiative trial — with an RR of 2.42 among those using the drugs for at least 5 years.The relative risks did not differ significantly among those using oral, transdermal or implanted formulations. Current use of HRT was also associated with an increased risk of death from breast cancer (RR = 1.22).Dr. Beral’s group estimates that approximately 20,000 extra breast cancers over the past decade can be attributed to women aged 50 to 64 who had used HRT, three-quarters of which were associated with the use of estrogen-progestin.In an accompanying editorial, Dr. Chris van Weel of University Medical Centre Nijmegen, The Netherlands, and colleagues recommend that general practitioners should discourage HRT for their patients. At most, they suggest, “a well-informed decision to prescribe HRT [should encompass] no longer than 3-6 months.”For those patients already taking HRT, they write, “Discontinuing HRT should be suggested in as supportive a way as possible, because no one will benefit from panic or over-reaction.”(Source: Lancet 2003;362:414-415,419-427: Reuters Health: August 7, 2003: Oncolink)