Prognostic value of Oncotype recurrence score (RS) and Mammaprint (MP) in premenopausal patients with hormone positive (HR+) breast cancer (BC) with low genomic risk, stratified by race: A study of the National Cancer Database (NCDB).

551 Background: It is hypothesized that in African American (AA) women, RS has a lower prognostic accuracy. We evaluated this with a large population based national database. Methods: The 2021 NCDB PUF was used to include premenopausal female BC patients aged 18-50 years. Inclusion criteria were N0, M0 patients with any T stage, RS ≤ 15 or MP low risk, estrogen or progesterone receptor+ and HER2-. Patients were stratified by their recorded race (Caucasians vs AA). Univariate analysis was used to study the distribution. Kaplan-Meier (KM) and multivariate (MV) propensity score (PS) weighted Cox model were used to compare survival between the cohorts. Results: 27523 patients had an RS≤15 Caucasian-25227(91.66%) AA-2296(8.34%) and 4818 had MP low Caucasian-4393(91.18%) AA-425(8.82%). >99% had regional lymph node surgery and >90% of the patients did not get chemotherapy. >70% of the patients were T1. Majority did get hormonal therapy (HT) RS≤15 Caucasian-92.97% AA-91.81%, MP low- Caucasian-92.42% AA-89.65%. On analyzing grade, AA had more poorly differentiated tumors RS≤15 Caucasian-6.18% AA-9.46% p=<0.001 MP low- Caucasian-9.1% AA-16.02% p=<0.001. KM survival estimates for RS≤15 at 5 years Caucasian-99.3(99.2,99.5) %, AA-98.8(98.0,99.3) % were similar and 10 years Caucasian-97.5(97.0,97.9) %, AA-94.6(91.6,96.6) showed a small difference. For MP low, the survival at 5 years Caucasian- 99.0(98.6,99.3) %, AA-98.9(97.0,99.6) % and 10 years Caucasian- 97.0(95.9,97.8) %, AA-95.8(91.0,98.1) % were almost equal. Adjusted Hazard Ratio estimate for Caucasian vs AA for RS≤15 did not reach significance overall 0.802 (95% CI 0.47-1.37) nor when stratified by grade, histology, or T stage. Conclusions: Through our analysis, we show that there was no major difference in overall survival between Caucasians and AA among low genomic risk, premenopausal, hormone positive, N0 BC patients. There was a 2.9% difference between the racial groups at 10 years, but this was not seen in the adjusted analysis. The results show that genomic scores like RS and MP retain their prognostic utility even in the low-risk spectrum in both Caucasians and AAs. These results differ from other database studies, where the utility of these tools in the low-risk AA groups were questionable. Confounding associated with retrospective studies could be contributing to this and the predictive ability of genomic scores in varied racial groups needs to be analyzed in prospective models.