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e12591 Background: Hormone receptor-positive, HER2-negative breast cancer (HR+/HER2- BC) has the highest incidence and mortality rate across all racial/ethnic groups. HR+/HER2- BC is clinically and biologically heterogenous. Gene expression profiling assays can provide prognostic information and predict risk of late recurrence among women with HR+/HER2- BC. Prior studies have shown worse clinical outcomes among black women with HR+/HER2- BC. We sought to compare the distribution of intrinsic subtypes among young black women with HR+/HER2- BC, compared to published data from a young white cohort in the Carolina Breast Cancer Study (CBCS). Methods: Two population-based cohorts of black women diagnosed with BC between 2002 to 2012 at or below age 50 years were analyzed. Participants were recruited from twelve Southeastern states. All participants were asked to complete release of medical records and tissue/tumor forms to verify clinical information and to obtain primary tumor samples for future analyses. We compared the distribution of intrinsic subtypes and associations to clinical characteristics as compared to white female counterparts using Pearson chi-squared test. Results: Of 569 black participants, 124 women had HR+/HER2- BC and tumor samples available for analysis. There were 66 Luminal A (53%), 35 Luminal B (28%), 19 Basal (15%), and 4 HER2-enriched (3%) tumors. Black women with non-Luminal A tumors were younger ( < 40) with larger tumors ( > 2cm) and had higher risk of recurrence (ROR-T) scores as compared to black women with Luminal A tumors (p = 0.065, 0.006, and < 0.001, respectively). Compared to young white women in the CBCS, black women in our study had a significantly higher percentage of non-Luminal HR+/HER2- BC (p = 0.037). Conclusions: Our results suggest that among young women with HR+/HER2- BC, black women have a higher proportion of non-Luminal tumors compared to their white counterparts. Non-Luminal HR+/HER2- tumors (i.e., basal and HER2-enriched) are more aggressive and may be less sensitive to endocrine therapy. These results suggest that overrepresentation of aggressive HR+/HER2- BC subtypes may contribute to the racial survival disparity observed among black women.

1579 Background: Per national practice guidelines, pre-test genetic counseling (GC) through a board-certified or credentialed genetics health professional (GHP) is recommended when testing for hereditary cancer. We sought to compare differences in rates of pre-test GC among young breast cancer (BC) patients tested with or without GHP involvement across three racial groups (Black, Hispanic and non-Hispanic white (NHW)). Methods: A population-based sample of Black, Hispanic and NHW women diagnosed with invasive BC ≤ age 50 from 2009 to 2012 were recruited through the Florida State Cancer Registry. Participants were asked to complete a baseline questionnaire and release medical records for verification of clinical information and genetic testing. We compared the rates of pre-test GC across racial groups in women tested with or without GHP involvement using Analysis of Variance. Multivariate logistic regression analysis was also conducted to adjust for potential confounders. Results: Of 1618 participants, 828 had genetic testing based on medical records and/or self-reported on their questionnaire. There were 170 (20.5%) with GHP involvement (either through consultation and/or test ordering) and the remaining 658 women (79.5%) had no documentation of GHP involvement. Among patients tested without GHP involvement, rates of pre-test GC were significantly lower among Black women (34.8%) compared to Hispanics (80%) and NHW (78.7%) (p < 0.001). In contrast, among those with GHP involvement, rates of pre-test GC were similar among Black (89.7%), Hispanic (81.1%) and NHW (84.6%) (p = 0.89). Conclusions: Our results suggest that among young breast cancer patients tested for hereditary cancer without GHP involvement, Blacks were significantly less likely to receive pre-test GC, compared to the other two groups. In contrast, rates of pre-test GC among those with GHP involvement were similar across all groups. These results suggest a disparity in receipt of pre-test GC (which is standard of care per national guidelines) among Blacks tested without GHP involvement. These findings are concerning given the need to offer guideline-adherent care to all patients receiving hereditary cancer testing.