Among the general population, parity decreases the risk of ovarian cancer by 45% compared with nulliparity. Subsequent pregnancies appear to decrease ovarian cancer risk by 15%. Earlier studies of women with BRCA1/BRCA2 mutations showed that parity decreases the risk of ovarian cancer.[196,200] In a large case-control study, parity was associated with a significant reduction in ovarian cancer risk in women with BRCA1 mutations, OR 0.67 (CI 0.46-0.96). For each birth, BRCA1 mutation carriers had an OR of 0.87 (CI 0.79-0.95). In this same study, parity was associated with an increase in ovarian cancer risk in BRCA2 mutation carriers; however, there was no significant trend for each birth, OR 1.08 (CI 0.90-1.29). Further studies are necessary to define the association of parity and risk of ovarian cancer in BRCA2 mutation carriers, but for BRCA1 carriers, each live birth significantly decreases risk of ovarian cancer, as it does in sporadic ovarian cancer.
Lactation and tubal ligation
In the general population, breast feeding is associated with a decrease in ovarian cancer risk. In BRCA mutation carriers, data are limited. One study found no protective effect with breast feeding. A case-control study among women with BRCA1 or BRCA2 mutations demonstrates a significant reduction in risk of ovarian cancer (OR = 0.39) for women who have had a tubal ligation. This protective effect was confined to those women with mutations in BRCA1 and persists after controlling for oral contraceptive use, parity, history of breast cancer, and ethnicity. A case-control study of ovarian cancer in Israel found a 40% to 50% reduced risk of ovarian cancer among women undergoing gynecologic surgeries (tubal ligation, hysterectomy, unilateral oophorectomy, ovarian cystectomy, excluding bilateral oophorectomy). The mechanism of protection is uncertain. Proposed mechanisms of action include decreased blood flow to the ovary, resulting in interruption of ovulation and/or ovarian hormone production; occlusion of the fallopian tube, thus blocking a pathway for potential carcinogens; or a reduction in the concentration of uterine growth factors that reach the ovary. (Refer to the PDQ summary on Prevention of Ovarian Cancer for information relevant to the general population.)
Refer to the Oral contraceptives section in the Chemoprevention section of this summary for more information.
Management of Male BRCA Mutation Carriers
There are data to suggest that men with BRCA gene mutations have an increased risk of various cancers including male breast cancer and prostate cancer (see Table 5).[180,203,204,205,206,207] However, clinical guidelines to manage male carriers with BRCA mutations are based on consensus statements and expert opinions because information is limited.[208,209,210]
There have been suggestions that BRCA2-associated prostate cancers are associated with aggressive disease phenotype.[211,212,213,214,215,216] Specifically, two recent studies have reported the median survival of male BRCA2 carriers with prostate cancer in the range of 4 to 5 years.[214,215] Furthermore, mortality rate was reported as 60% at 5 years in one of these studies, compared with 2% to 8% reported in the recent European  and North American  PSA screening trials after comparable follow-up. The data have been more limited in BRCA1-associated prostate cancers, however a number of recent studies have suggested an aggressive disease phenotype as well.[211,213,216,219]