Abstract A019: Black race and CA 19-9 nonproduction is associated with limited pathologic response to neoadjuvant chemotherapy in patients with localized pancreatic cancer

Abstract Introduction: Black patients with pancreatic ductal adenocarcinoma (PDAC) are less likely to have major pathologic response (MPR) following induction chemotherapy. Our previous study suggested a lower baseline CA 19-9 among Black patients. We aimed to determine if CA 19-9 nonproduction contributes to racial differences in neoadjuvant chemotherapy (NAC) response. We then investigated the biological mechanisms underlying reduced response in CAnonprod with multi-omic analysis. Methods: Black and White patients with PDAC receiving ≥ 2 cycles of NAC followed by pancreatectomy at 7 high-volume centers were reviewed. Patients were categorized as CAproducers (CAprod, CA 19-9 > 5 U/mL) or CAnonprod (CA 19-9 ≤ 5 U/mL). Uni- and multi-variable models evaluated differences in rates of CAnonprod by race, and the association of CAnonprod with MPR (CAP 0/1). The Pancreatic Cancer Action Network SPARK platform was queried for patients with CA 19-9 and genomic data. Fisher’s exact test was used to compare differentially mutated genes between CAnonprod and CAprod. Differential gene expression (DEG) analysis identified significantly differentially expressed genes using an absolute fold change of ≥ 2 and p-adj < 0.05 as a cutoff. quanTIseq computational pipeline was used for immune cell deconvolution analysis of the two groups. Results: Our cohort included 385 CAprod and 30 CAnonprod. CAnonprod had a significantly higher rate of Black patients (50% vs 13%, p<0.01). Compared with CAprod, CAnonprod received similar rates of FOLFIRINOX (60% vs. 57%, p=0.27) and duration of NAC (4 vs 5 cycles, p=0.83). Rate of MPR was higher among CAprod compared to CAnonprod (26% vs 8%, p=0.03). No CAnonprod patient had a complete pathologic response vs 28 (7%) of CAprod (p=0.12). CAnonprod was independently associated with decreased odds of MPR (OR 0.21, CI [0.04-0.99]). Black race was independently associated with increased odds of CAnonprod (OR 8.66, CI [3.81 – 19.7]). When CA 19-9 production status was matched by race, there was no difference between rate of MPR between White and Black CAnonprod; both experienced low rates of MPR (12% and 9%, respectively, (p=0.68)). CAnonprod had higher rates of SWI/SNF alterations (50% CAnonprod vs 33% CAprod, p< 0.01; P-adj=ns), and ARID1B was the most frequently mutated gene in CAnonprod (28% vs 11%, p< 0.01; P-adj=ns). DEG analysis showed the LIPF gene was significantly downregulated in CAnonprod compared to CAprod. There was no difference in immune cell distribution between CAprod and CAnonprod. Conclusion: CA 19-9 non-production is more prevalent in Black patients and potentially mediates the lower rates of MPR following NAC. CA 19-9 non-production is associated with higher rates of SWI/SNF alterations and a downregulation of the LIPF gene encoding gastric lipase, unveiling a potential biologic or metabolomic difference in response to chemotherapy between races. Citation Format: Mary P. Martos, Erin M. Dickey, Kawther Abdilleh, Syed A. Ahmad, Shishir K. Maithel, Chet W. Hammill, Hong Jin Kim, Daniel E. Abbott, David A. Kooby, Alexander A. Parikh, Peter J. Hosein, Nipun B. Merchant, Jashodeep Datta, Caitlin A. Hester. Black race and CA 19-9 nonproduction is associated with limited pathologic response to neoadjuvant chemotherapy in patients with localized pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr A019.