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Hormone replacement therapy does not appear to increase the risk of breast cancer recurrence, but more studies are needed

Most of the 2.5 million women who have survived breast cancer in the United States are menopausal. Also, 70 percent of women who develop breast cancer in their reproductive years develop premature menopause from chemotherapy used to treat the cancer. Declining estrogen levels cause many of these women to suffer from hot flashes, mood and sleep disturbances, memory impairment, and sexual dysfunction; in addition, their risk of osteoporosis increases. Hormone replacement therapy (HRT) that can alleviate these symptoms is typically withheld from women who have had breast cancer because of concern that it might increase the risk of cancer recurrence.

A new study, supported in part by the Agency for Healthcare Research and Quality (HS09796), suggests that HRT does not increase the risk of cancer recurrence, but Joseph Lau, M.D., of the New England Medical Center, and his colleagues call for further studies to confirm their findings. They based their findings on a systematic review of research studies through May 1999.

The researchers calculated the relative risk of breast cancer recurrence in each study by comparing the number of recurrences in the HRT group to those in the non-HRT group. Of the 11 eligible studies, 4 had non-HRT control groups and included 214 breast cancer survivors who began HRT after a mean disease-free interval of 52 months. Over a mean followup of 30 months, 4.2 percent of HRT users per year compared with 5.4 percent of nonusers experienced a recurrence of breast cancer. Including all 11 studies in the analyses (669 HRT users) and using estimated control groups for the 7 uncontrolled trials did not significantly change the results.

Although these findings do not exclude the possibility that HRT might increase the risk of recurrence, they suggest that it is unlikely that the magnitude of risk is large. Nonetheless, many women may not be willing to tolerate even a relatively small increase in their risk of breast cancer recurrence to obtain the benefits of HRT. While waiting for results of ongoing randomized clinical trials, doctors should inform women with breast cancer who are interested in taking HRT about the uncertain effects of HRT on recurrence risk, conclude the researchers.

More details are in "Hormone replacement therapy after breast cancer: A systematic review and quantitative assessment of risk," by Nananda F. Col, M.D., Linda K. Hirota, Richard K. Orr, and others, in the April 15, 2001, Journal of Clinical Oncology 19, pp. 2357-2363.

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