Performance of BRCA1/2 mutation prediction models in Asian Americans.

PURPOSE: There are established differences in breast cancer epidemiology between Asian and white individuals, but little is known about hereditary breast cancer in Asian populations. Although increasing numbers of Asian individuals are clinically tested for BRCA1/2 mutations, it is not known whether computer models that predict mutations work accurately in Asian individuals. We compared the performance in Asian and white individuals of two widely used BRCA1/2 mutation prediction models, BRCAPRO and Myriad II. PATIENTS AND METHODS: We evaluated BRCAPRO and Myriad II in 200 Asian individuals and a matched control group of 200 white individuals who were tested for BRCA1/2 mutations at four cancer genetics clinics, by comparing numbers of observed versus predicted mutation carriers and by evaluating area under the receiver operating characteristic curve (AUC) for each model. RESULTS: BRCAPRO and Myriad II accurately predicted the number of white BRCA1/2 mutation carriers (25 observed v 24 predicted by BRCAPRO; 25 predicted by Myriad II, P > or = .69), but underpredicted Asian carriers by two-fold (49 observed v 25 predicted by BRCAPRO; 26 predicted by Myriad II; P < or = 3 x 10(-7)). For BRCAPRO, this racial difference reflects substantial underprediction of Asian BRCA2 mutation carriers (26 observed v 4 predicted; P = 1 x 10(-30)); for Myriad II, separate mutation predictions were not available. For both models, AUCs were nonsignificantly lower in Asian than white individuals, suggesting less accurate discrimination between Asian carriers and noncarriers. CONCLUSION: Both BRCAPRO and Myriad II underestimated the proportion of BRCA1/2 mutation carriers, and discriminated carriers from noncarriers less well, in Asian compared with white individuals.

Ductal carcinoma in situ in BRCA mutation carriers.

PURPOSE: The current literature suggests that ductal carcinoma in situ (DCIS) of the breast is infrequently diagnosed in patients with BRCA germline mutations. We studied women at high risk of hereditary breast cancer syndromes who underwent testing for BRCA1 and BRCA2 to estimate DCIS prevalence and incidence in known BRCA-positive women compared with high-risk women who were mutation negative. METHODS: We analyzed breast event outcomes in a retrospective cohort of 129 BRCA-positive and 269 BRCA-negative women undergoing genetic testing for a BRCA mutation between September 1996 and December 2003 at University of California, San Francisco. We estimated the frequency of DCIS and invasive cancer and time to breast events from birth using a Cox proportional hazard model for competing risks. Histologic grade of DCIS was also compared between groups. RESULTS: Among BRCA carriers, 48 (37%) had DCIS (with or without invasive cancer) compared with 92 noncarriers (34%). Univariate analysis showed that both DCIS and invasive cancer had an earlier onset in mutation carriers than in noncarriers, although on a per-woman basis, this difference was not statistically significant. High-grade DCIS was more common in BRCA1 mutation carriers than in patients without a mutation (P = .02). CONCLUSION: DCIS is equally as prevalent in patients who carry deleterious BRCA mutations as in high familial-risk women who are noncarriers, but occurs at an earlier age. Our results argue for the consideration of DCIS as a criterion for BRCA risk assessments with appropriate weighting in prediction models such as BRCAPRO.