MELBOURNE, AUSTRALIA. Many women over 50 years of age are prescribed hormone replacement therapy (HRT) in order to ameliorate menopause symptoms and prevent excessive loss of bone mass. Unfortunately, HRT has been associated with an increased risk of breast cancer. It is therefore important that women on HRT be checked for breast tumors at periodic intervals. Public health authorities in most developed countries recommend screening with mammography every one or two years for women over the age of 50 years. Australian researchers now report that mammography is less accurate in women on HRT than in women not on HRT. Their study involved 103,770 women in the state of Victoria who had a mammogram for the first time in 1994. The use of HRT among these women varied from 20.2 per cent in those aged 40-49 years to almost 40 per cent in women aged 50-59 years. The detected incidence of breast cancer among women in the 50-59 year age group was 0.33 per cent (141 cases out of 43,090) for women not on HRT as compared to 0.58 per cent (100 cases out of 17,209) for women on HRT.
Unfortunately, the sensitivity of the screening was found to be significantly poorer in the
case of women on HRT. In the age group 50-69 years (the most vulnerable group) the
sensitivity (percentage of actual cancers detected) of mammography was only 64.3 per
cent among HRT users as compared to 79.8 per cent among non-users. So not only does
HRT use increase the risk of breast cancer, but it also makes it significantly harder to
detect. The researchers suggest that women on HRT may wish to discontinue therapy for
a brief period before mammography and also recommend that women be told about the
lack of accuracy of mammography in HRT users when they are faced with the decision
about whether to start HRT.