A recently published article by Nichols and colleagues  provides a detailed analysis of data collected from 10,449 women with invasive breast cancer compared to 11,787 age-matched controls without breast cancer to determine whether the use of estrogen therapy following a bilateral oophorectomy prior to reaching a natural menopause had any influence on the development of breast cancer. In pooled data from the Collaborative Breast Cancer Studies population-based, case–control studies collected between 1992 and 2007, the use of estrogen prescribed for women, following total abdominal hysterectomy with bilateral salpingo-oophorectomy, was analyzed for subsequent development of breast cancer. Case participants were compared with age-matched control cohorts obtained by identifying women in a register of licensed drivers or from a list of Medicare beneficiaries.
A very confusing picture emerges from the results.
1. All women who had their ovaries removed before the age of 40 years were found to have a decreased risk of developing breast cancer – a 24% reduction following estrogen use and 30% reduction when no hormone was used.
2. Women over the age of 45 years when their ovaries were removed were found to have no reduction in the risk of breast cancer if they used estrogen therapy (but no increased risk).
3. Those women who began estrogen therapy within 5 years of bilateral oophorectomy had a 22% increased risk of breast cancer, whereas those who delayed estrogen use for 5 or more years had a 54% reduction in the risk of breast cancer.
4. Among current estrogen users, those women taking the hormone for less than 10 years had a 32% increased risk of breast cancer, whereas those using estrogen for longer than 10 years had no significant increase in breast cancer.
5. Among current users of estrogen therapy, those who were younger when beginning therapy had a decreased risk of breast cancer while there was an overall increase in breast cancer for older women on estrogen.
Gynaecological Endocrinologist, Edgecliff Centre, Edgecliff, NSW, Australia
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