NEW YORK (Reuters Health), Oct 16 - Benign ovarian cysts do not increase the risk of breast cancer, according to results of a meta-analysis of case-control studies conducted in Italy and Switzerland. In fact, benign cysts were associated with a 30% decreased risk of breast cancer, the investigators report.
Benign ovarian cysts are associated with infertility and menstrual cycle irregularities, Dr. Cristina Bosetti and colleagues explain in their report, published in the International Journal of Cancer for October. On that basis, it has been suggested that ovarian cysts may alter hormone levels that in turn could influence breast cancer risk.
Population-based and case-control studies have failed to either support or refute that theory. Therefore, Dr. Bosetti, from Instituto di Ricerche Farmarmacologiche Mario Negri in Milan, Italy, and her team pooled data from two hospital-based case-control studies conducted in Italy between 1983 and 1991 and between 1991 and 2001, as well as one performed between 1992 and 2001 in Switzerland.
The researchers included 6,315 cases of breast cancer and 6,315 control subjects admitted to the same hospitals for unrelated reasons in their analysis. The subjects had been interviewed while hospitalized regarding sociodemographic, menstrual and reproductive factors, including a history of ovarian cysts.
Combined data showed that 4.9% of cancer cases and 6.6% of controls reported a history of ovarian cysts (multivariate odds ratio of 0.72), Dr. Bosetti and her associates report.
The inverse association between ovarian cysts and breast cancer was strongest among women with atypical menstrual cycles, those who had never used oral contraceptives, those who undergone bilateral oophorectomy or hysterectomy, and those with lower BMI.
The relationship also remained after stratification according to age at menarche, parity, age at menopause, and family history of breast cancer.
These findings prompted the investigators' conclusion that, "although some hormonal correlates of ovarian cysts may have a role on breast cancer risk, a biological explanation of this association is still unclear."
Last Updated: 2006-10-13 14:20:17 -0400 (Reuters Health)
Int J Cancer 2006;119:1679-1682.
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