Abstract 3784: Methylated DNA markers for detection of peritoneal metastasis in pancreatic cancer

Abstract

Abstract Introduction: Laparoscopy with peritoneal lavage enhances staging accuracy in patients with pancreatic ductal adenocarcinoma (PDAC). Occult intra-abdominal metastases are identified by staging laparoscopy in approximately 20% of patients with radiologically localized PDAC. Peritoneal fluid cytology has limited sensitivity in detecting occult intra-abdominal metastasis. Methylated DNA markers (MDMs) can accurately detect PDAC from tumor tissue, blood, and pancreatic secretions. This study aims to assess the feasibility of assaying MDMs in peritoneal lavage fluid obtained at the time of staging laparoscopy for patients with PDAC. Methods: Peritoneal lavage fluid (25-60 mL) obtained from patients with PDAC at the time of staging laparoscopy was centrifuged for 10 minutes at 1200 × g. The pellet was resuspended and aliquoted into 200µL tubes and frozen at -80°C. DNA extracted from one aliquot was assayed for mutant KRAS (G12A and G13D) and then bisulfite converted to measure 13 MDMs (GRIN2D, CD1D, ZNF781, FER1L4, RYR2, CLEC11A, AK055957, LRRC4, MAX.CHR5.4295, HOXA1, PRKCB, SHISA9, NTRK3) and a normalizing reference gene (B3GALT6) using quantitative methylation specific PCR. The association of KRAS and the average signal from the 13 MDMs (MDMscore) with intra-abdominal metastasis (Y/N) was assessed with the area under the receiver operator characteristic curve (AUC). Results: Among 48 PDAC patients, staging laparoscopy revealed intra-abdominal metastasis in 15 (31%). Of the 15 intra-abdominal metastases, 6 were found to have biopsy-confirmed intra-abdominal metastasis and positive peritoneal cytology, 4 were positive on peritoneal cytology alone, and 5 had biopsy-confirmed intra-abdominal metastasis alone. The sensitivity of the MDMscore for intra-abdominal metastasis was 87% (CI: 60-98%) at 90% (CI: 76-98%) specificity whereas the sensitivity for KRAS was 40% (CI: 16-68%) at 85% (CI: 68-95) specificity. The AUC for the MDMscore was 0.98 (CI: 0.94-1.00) compared to 0.62 (CI: 0.48-0.77) for that of KRAS (p<0.0001). Conclusion: MDMs assayed from peritoneal lavage fluid collected during staging laparoscopy is a novel tool for accurate molecular staging of PDAC. These early results warrant further study in a larger cohort to assess impact on peritoneal staging and its clinical utility in the neoadjuvant treatment paradigm of PDAC. Citation Format: Kalika Maheshwari, Calise K. Berger, William R. Taylor, Douglas W. Mahoney, Kelli N. Burger, Adriana M. Delgado, Karen A. Doering, Heather M. Streich, Patrick H. Foote, Sean P. Cleary, Travis E. Grotz, Micheal L. Kendrick, Rory L. Smoot, Patrick P. Starlinger, Cornelius A. Thiels, Mark J. Truty, Susanne G. Warner, John B. Kisiel, Shounak Majumder. Methylated DNA markers for detection of peritoneal metastasis in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3784.