Hormone Replacement Therapy Increases the Risk of Breast Cancer
One of the most alarming findings of the National Institutes of
Health (NIH) Women's Health Initiative (WHI) last year was the significant increase
in the risk of invasive breast cancer among menopausal women who took combined
conjugated equine estrogen and medroxyprogesterone acetate therapy (Prempro™).
These data were at least reassuring (although confusing) in that there was
no difference in mortality between the treatment group and the placebo group.
The Million Woman Study recently published in the British medical journal
the Lancet (8/03) compounds the WHI data. In this study, women receiving
a combination of estrogen and progestin not only had an increased risk of breast
cancer, but they had a 22% higher risk of death from breast cancer compared
with women who weren't receiving hormonal therapy.
The Million Woman Study surveyed 1.1 million women
in the United Kingdom aged 50 to 64. They were recruited between 1996 and 2001
and tracked for cancer incidence and death.
Based upon existing statistical data, we know that out of 1,000
postmenopausal women between the ages of 50 and 60 who don't use HRT, there
will be approximately 20 breast cancer cases diagnosed. However, according to this study,
in every 1,000 women who begin 10 years of HRT at the age of 50, there will
be five extra cases among estrogen-only users, and 19 additional breast
cancers among estrogen-progestin combination users.
These data are consistent with the WHI data in that the group of women on combined
HRT fared worse than the group of women on estrogen alone. This raises many
questions, including whether women currently taking either of these treatment
regimens should make changes. As always, these decisions should be based upon
consultation with your personal physician rather than a rash interpretation
of how a clinical trial might apply to you.
Created: 9/4/2003  - Donnica Moore, M.D.