TUESDAY, Dec. 30 (HealthDay News) -- Long-term use of certain types of hormone replacement therapy is associated with an increased risk of breast cancer, according to two studies published in the January issue of Obstetrics & Gynecology.
Heli Lyytinen, M.D., of the Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research in Helsinki, Finland, and colleagues conducted a study of 221,551 Finnish women using E2-progestogen therapy for six months or more, and found that after three years of use it increased the risk of breast cancer.
Susan S. Jick, of Boston University School of Medicine in Lexington, Mass., and colleagues analyzed US claims data to identify 4,515 cases of breast cancer and 18,058 matched controls. They found that although women using estrogen alone or esterified estrogen with methyltestosterone were at no more risk of breast cancer than non-users, women who used conjugated estrogen combined with progestin were at higher risk than non-users, particularly those who were on hormone replacement therapy for four or more years, which approximately tripled the risk compared to non-users.
"The risk of breast cancer in women who used conjugated estrogen plus progestin for four or more years is approximately three times higher than in women who are not exposed to hormone therapy, so that the background incidence rate for women aged 50 to 64 years, which is around three per 1,000, would be increased to approximately nine per 1,000 in women aged 50 to 64 years who have taken conjugated estrogen plus progestin for 48 months or more," Jick and colleagues write.
The first study was supported by BayerHealthCare. The second study was supported by Solvay Pharmaceuticals.
Abstract - Lyytinen
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Abstract - Jick
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