What are the Breast Cancer Risks from using Replacement Hormones
A. From the Journal of Obstetrics/Gynecology, Dec 2006 pp 1354-60
B. Study involving Finnish women using a synthetic estrogen, Estradiol, either orally or transdermally
1. During 648,022 patient-years of observation, there were 2,171 cases of reported breast cancer.
2. The researchers came up with a (SIR),standardized incidence ratio, by comparing the observed number of new breast cancers to the expected number of new breast cancers, based on the average incidence of breast cancer in Finnish women.
3. Estradiol use for more than 5 years was associated with an increased risk of breast cancer (SIR=1.44)
4. The risk was also elevated for women who used the Estradiol for less than 5 years (SIR=0.923 to 1.30)
5. The researchers were concerned by the likelihood that many of the women could have been taking replacement estrogen prior to the initiation of the study.
6. The SIR increased with the daily dose of estrogen.
7. Use of estrogen patches or transdermal preparations was also associated with increased SIRs.
8. The use of synthetic estrogen, Estradiol, for 5 or more years is associated with 2-3 additional cases of breast cancer per 1,000 women during a 10 year follow up.