Evidence on risk of breast cancer associated with hormone replacement therapy is still inconclusive

EDITOR,—As a female doctor who has a specialist interest in the menopause and hormone replacement therapy, I was interested to read Elizabeth H Price and Helen Kaye Little's letter about hormone replacement therapy.1 I agree that women need to be informed about the risks associated with such treatment. I disagree, however, with the authors' statements about the increased risk of breast cancer.

The epidemiological evidence on the effect of combined treatment with oestrogen and progestin on the risk of breast cancer is still too limited to be conclusive: neither a protective nor a detrimental effect has been reliably shown. The largest case-control study (from the Centers for Disease Control2), the largest cohort follow up study (the nurses' health study3), and the most recent case-control study4 failed to find a link between breast cancer and use of oestrogen up to 20 years. Lower doses of oestrogen, which protect against osteoporosis and cardiovascular disease, are not known to be associated with an increased risk of breast cancer. A recent meta-analysis detected a small increased relative risk of breast cancer being diagnosed in women taking combined oral contraceptives.5 This study, however, was not free of selection and detection bias or of the risk of a positive result emerging owing to the heterogeneity of the studies included. Only a randomised clinical trial will provide definitive information on this issue.

It is my practice to give patients evidence based information about the risks and benefits of hormone replacement therapy. The evidence overwhelmingly supports the protective effects of such treatment on the cardiovascular system and against osteoporosis; it remains equivocal on the risks of breast cancer. I do not believe that it is appropriate to make either positive or negative statements about the effects of hormone replacement therapy on health on the basis of single references, as Price and Little do. No treatment is without risk, and I regard my patients as responsible adults who will make their own decisions on the basis of the best information I can provide. I encourage the provision of information by groups such as DASH (Doctors Against Abuse from Steroid Sex Hormones)1 if that information is complete and unbiased.