Prophylactic oophorectomy reduces breast cancer penetrance during prospective, long-term follow-up of BRCA1 mutation carriers.
OBJECTIVE
Breast cancer penetrance estimates in BRCA1 mutation carriers have varied from 40% to 85%; this heterogeneity has been attributed to variations in risk among different study populations. No study has taken oophorectomy status into account in estimating penetrance. Because prophylactic oophorectomy reduces breast cancer risk by approximately 50%, we hypothesized that population differences in oophorectomy prevalence might significantly influence breast cancer penetrance estimates.


METHODS
Females from multiple-case breast/ovarian cancer families that segregate deleterious BRCA1 mutations were observed prospectively for breast cancer incidence and oophorectomy.


RESULTS
Within this cohort, 33 cases of breast cancer developed in 98 women with deleterious BRCA1 mutations during follow-up, yielding an estimated cumulative lifetime breast cancer risk of 80%. This estimate increased to 94% when the study participants were censored at the time of oophorectomy. Six of the 33 mutation-positive women who underwent oophorectomy during follow-up developed breast cancer, compared with 27 of 65 mutation carriers with intact ovaries (hazard ratio = 0.38; 95% CI, 0.15 to 0.97). Estimates of absolute breast cancer risk demonstrated that the protective effect of oophorectomy was strongest among women who were premenopausal at the time of surgery. When surgical status was ignored, the strong protective effect of oophorectomy, coupled with the high prevalence of the procedure in these families, led to a significantly lower estimate of the breast cancer penetrance in BRCA1 mutation carriers.


CONCLUSIONS
Differing rates of oophorectomy likely represent an underappreciated basis for a portion of the heterogeneity in estimated breast cancer penetrance described in BRCA mutation carriers, particularly mutation carriers from extensively affected, multiple-case families.
Kramer
Joan L
JL
Clinical Genetics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, 6120 Executive Blvd, Room 7016, MSC 7231, Rockville, MD 20852, USA. kramerj@mail.nih.gov
Velazquez
Isela A
IA
Chen
Bingshu E
BE
Rosenberg
Philip S
PS
Struewing
Jeffery P
JP
Greene
Mark H
MH
D000328:Adult; D000367:Age Factors; D000368:Aged; D019313:BRCA1 Protein / Q000235:genetics*; D001943:Breast Neoplasms / Q000235:genetics* / Q000517:prevention & control; D005192:Family Health; D005260:Female; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease / Q000235:genetics; D018095:Germ-Line Mutation / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000235:genetics / Q000601:surgery; D010052:Ovariectomy; D019683:Penetrance; D011446:Prospective Studies; D012307:Risk Factors; D013997:Time Factors
D019313:BRCA1 Protein