Model-based predictions of BRCA1/2 mutation status in breast carcinoma patients treated at an academic medical center.

BACKGROUND: Women with an existing breast carcinoma diagnosis who are found to carry a BRCA1/2 mutation have a substantial risk of developing both a contralateral breast carcinoma and ovarian carcinoma. In a newly diagnosed breast carcinoma patient, this genetic information may influence the management of her disease. To assess the volume of patients who may need genetic services at the time of diagnosis, the authors determined the proportion of women with newly diagnosed breast carcinoma at the study institution who would be eligible for genetic testing.
METHODS: Fifty consecutive women with new breast carcinoma who were attending a multidisciplinary clinic were interviewed. Detailed, three-generation pedigrees were collected for each patient by a genetic counselor. Three commonly used probability models were used to calculate each woman's predicted risk of harboring a germline BRCA1/2 mutation.
RESULTS: Eleven of 50 patients (22% [95% confidence interval, 12-36%]) were calculated to have a > or = 10% probability of carrying a BRCA1/2 mutation by at least one mathematic model and should have been offered genetic counseling that included the discussion of genetic testing. There were considerable discrepancies between probability calculations among the three mathematic models. One of the 11 patients who was eligible for genetic testing pursued genetic counseling within 12 months of diagnosis.
CONCLUSIONS: At a large academic medical center, a substantial proportion of unselected women attending a multidisciplinary clinic were found to have a > or = 10% risk of carrying a BRCA1/2 mutation. The actual number of patients eligible to receive BRCA1/2 genetic testing outweighs the number of patients seen for genetic counseling at the study institution. Finally, limited correlation was found between current predictive models.