Association of ImPrintTN signature with survival outcomes by race in basal-type triple negative breast cancer (TNBC): FLEX registry analysis.

554 Background: ImPrintTN is a triple negative breast cancer (TNBC) immune classifier signature that has been associated with pathological complete response (pCR) to immunotherapy (IO) plus chemotherapy in ISPY2. Real Word data (RWD) from FLEX was utilized to assess the association of ImPrintTN with self-reported race and its impact on clinical outcomes in early stage TNBC. Methods: Patients (pts) enrolled in the FLEX (NCT03053193) trial diagnosed with early-stage TNBC and BluePrint Basal molecular subtype with available survival data, who self-identified as Black or White, were eligible for this analysis. ImPrintTN results (+/-) were acquired through whole transcriptome profiling. Chi-squared and Fisher’s exact tests assessed differences in clinical characteristics. Association of pCR outcomes and ImPrintTN+/- were tested by binary logistic regression. Recurrence-free survival (RFS) was compared between race and ImPrintTN+/- using Kaplan-Meier estimates and log rank tests. Cox proportional hazards model was used to analyze the association of ImPrintTN, race, and clinical features with RFS. Results: Among 279 eligible patients with early stage Basal TNBC, 23.7% were Black, 76.3% were White, 27.7% had node positive disease, 49.8% received neoadjuvant therapy, 47.3% adjuvant therapy, 2.5% IO, and median follow-up was 3 years. 56.6% of pts were ImPrintTN+, similarly distributed by race (Black: 60.6%, White: 55.4%, p=0.761). Among pts treated with neoadjuvant therapy (n=139) no significant differences in pCR rates were observed by race (Black: 26.5%; White: 35.2%; p=0.46). However, a higher pCR rate was achieved in ImPrintTN+ vs ImPrintTN- cancers (39.3% vs 22.0%; OR=2.29, 95% CI [1.04-5.08]; p=0.039). The 3-year RFS was similar for Black (82.5%) and White (83.5%; p=0.91) pts. Significantly improved 3-year RFS was associated with ImPrintTN+ (87.9%) compared to ImPrintTN- (77.5%; p=0.01). Among ImPrintTN+, RFS was similar for Black (89.7%) and White (87.3%; p=0.30) pts. However, ImPrintTN- observed a trend towards lower 3-year RFS in Black (71.1%) compared with White (79.2%; p=0.24) pts. In a multivariate model, RFS probability was significantly associated with ImPrintTN (ImPrintTN+ vs ImPrintTN-: HR= 0.41, 95% CI [0.22-0.75]; p=0.004) and nodal status (LN+ vs LN-: HR= 2.98, 95% CI [1.66-5.37,]; p<0.001), while race and neo/adjuvant therapy were not. Conclusions: The analysis found that 56.6% of Basal TNBCs in the FLEX trial were ImPrintTN+, with similar proportions observed among Black and White pts. ImPrintTN status was prognostic for both pCR and RFS in TNBC and was associated with significantly improved RFS across racial groups. However, the negative prognostic impact of ImPrintTN- appeared more pronounced among Black compared with White pts. Ongoing research is focused on exploring biological differences within the ImPrintTN- subgroup by race. Clinical trial information: NCT03053193 .