Incremental impact of breast cancer SNP panel on risk classification in a screening population of white and African American women

Abstract

Breast cancer risk prediction remains imperfect, particularly among non-white populations. This study examines the impact of including single-nucleotide polymorphism (SNP) alleles in risk prediction for white and African American women undergoing screening mammogram. Using a prospective cohort study, standard risk information and buccal swabs were collected at the time of screening mammography. A 12 SNP panel was performed by deCODE genetics. Five-year and lifetime risks incorporating SNPs were calculated by multiplying estimated Breast Cancer Risk Assessment Tool (BCRAT) risk by the total genetic risk ratio. Concordance between the BCRAT and the combined model (BCRAT + SNPs) in identifying high-risk women was measured using the kappa statistic. SNP data were available for 810 women (39 % African American, 55 % white). The mean BCRAT 5-year risk was 1.71 % for whites and 1.18 % for African Americans. Mean genetic risk ratios were 1.09 in whites and 1.29 in African Americans. Among whites, three SNPs had higher frequencies, and among African Americans, seven SNPs had higher and four had lower high-risk allele frequencies than previously reported. Agreement between the BCRAT and the combined model was relatively low for identifying high-risk women (5-year κ = 0.54, lifetime κ = 0.36). Addition of SNPs had the greatest effect among African Americans, with 12.4 % identified as having high-5-year risk by BCRAT, but 33 % by the combined model. A greater proportion of African Americans were reclassified as having high-5-year risk than whites using the combined model (21 vs. 10 %). The addition of SNPs to the BCRAT reclassifies the high-risk status of some women undergoing screening mammography, particularly African Americans. Further research is needed to determine the clinical validity and utility of the SNP panel for use in breast cancer risk prediction, particularly among African Americans for whom these risk alleles have generally not been validated.