An inverse association between ovarian cysts and breast cancer in the breast cancer family registry

Abstract

Ovarian cysts of several types are common in women of reproductive age. Their etiology is not well understood but is likely related to perturbations in the hypothalamic-pituitary-gonadal axis. The relationship of ovarian cysts to breast cancer risk is not known, although a negative association with polycystic ovarian syndrome has been reported. Incident, invasive female breast cancer cases, population-based controls and unaffected sisters of cases were studied from 3 countries participating in the Breast Cancer Family Registry: Melbourne and Sydney, Australia; the San Francisco Bay Area, USA; and Ontario, Canada. Using the same questionnaire, information was collected on self-reported history of ovarian cysts and other risk factors. Analyses were based on 3,049 cases, 2,344 population controls and 1,934 sister controls from all sites combined. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using both unconditional and conditional logistic regression using an offset term to account for sampling fractions at 2 of the sites. A significantly reduced risk of breast cancer was observed for women reporting a history of ovarian cysts (OR 5 0.70, 95% CI 0.59-0.82, among all cases and all controls). This risk estimate was similar regardless of control group used, within all 3 sites and in both premenopausal and postmenopausal women (ORs ranging from 0.68-0.75, all 95% CI excluded 1.00). A self-reported history of ovarian cysts was strongly and consistently associated with a reduced risk of breast cancer. Further study of ovarian cysts may increase our understanding of hormonal and other mechanisms of breast cancer etiology. ' 2005 Wiley-Liss, Inc.

Benign ovarian cysts and breast cancer risk

“…Similar reduced risks were found in pre-and postmenopausal women. This finding confirms the results from another case-control study, 10 although the evidence is not totally consistent.…”

“…9 Consequently, ovarian cysts that lead to bilateral oophorectomy are inversely related to breast cancer risk. However, a population-based case-control study from Australia, Canada and the USA, 10 including 3,049 breast cancer cases, found a significant reduced risk of breast cancer (odds ratio, OR 5 0.7), even in women who had not undergone oophorectomy. Conversely, a nonsignificant 20% increased risk of breast cancer was reported in another US population-based case-control study including 2,173 cases, 11 the association being limited to women with ovarian cysts who had not undergone oophorectomy (OR 5 1.9).…”

“…10 This may reflect real differences in the frequency of the disease, but also different diagnostic attitudes towards minor gynaecological conditions in various populations. If this is the case, our data should include more clinically relevant diseases, which require medical attention.…”

Medical radiation exposure and breast cancer risk: Findings from the Breast Cancer Family Registry

“…[26][27][28] Cases were ascertained through the regional population-based cancer registries, using center-specific eligibility and sampling criteria. In Australia, incident breast cancer cases were sampled according to age at diagnosis, whereas in Ontario a two-stage sampling design was used to over-sample cases likely to be at increased genetic risk of breast cancer (i.e., cases diagnosed at a young age or with a family history of cancer).…”

Ovarian cysts and breast cancer: results from the Women’s Contraceptive and Reproductive Experiences Study

“…Initial reports were largely null [1][2][3], but two recent studies with larger samples have reported a reduced risk of breast cancer significantly associated with a diagnosis of ovarian cysts [4,5].…”