• Jennifer A Yonkus, Roberto Alva-Ruiz, Amro M Abdelrahman, Jennifer L Leiting, Amber R Schneider, Travis E Grotz, Sean P Cleary, Rory L Smoot, David M Nagorney, Michael L Kendrick, Benjamin R Kipp, and Mark J Truty.
• Section of Hepatobiliary and Pancreatic Surgery, Division of Subspecialty General Surgery, Department of Surgery.
• J. Am. Coll. Surg. 2021 Jul 1; 233 (1): 73-80.e1.

BackgroundPancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with predilection for peritoneal dissemination. Accurate peritoneal staging is imperative for treatment recommendations, as one-third of patients develop peritoneal recurrence after resection. Because >90% of PDAC tumors harbor mutant KRAS (mKRAS), we sought to determine feasibility of mKRAS DNA detection in peritoneal lavage (PL) fluid using droplet-digital polymerase chain reaction (ddPCR) via a prospective trial.Study DesignPatients with nonmetastatic PDAC undergoing staging laparoscopy with PL were included. PL fluid was sent for cytologic examination, CA19-9/CEA levels, and mKRAS ddPCR assay. Clinically positive laparoscopy was defined as gross metastases or positive cytology. PL mKRAS status was compared with gross findings, cytology, and CA19-9/CEA levels.ResultsThere were 136 patients enrolled; 70 of 136 (51%) patients received neoadjuvant therapy before PL, and 32 of 136 (24%) patients had clinically positive laparoscopy. Cytology was positive in 17 of 136 (13%) patients, and 22 of 136 (16%) patients had gross metastases. Of patients with gross metastases, only 8 of 22 (36%) had positive cytology; 97 of 136 (71%) patients had mKRAS in PL. PL mKRAS was present in 27 of 32 (84%) clinically positive laparoscopies, with higher mean copy number in clinically positive patients (643 vs 10, p = 0.02). Peritoneal mKRAS was positive in an additional 70 clinically negative patients.ConclusionsThis prospective study establishes the feasibility of PL mKRAS detection. Clinically positive disease was identified in 1 in 4 staging laparoscopies. Although PL mKRAS was highly associated with clinically positive findings, many clinically negative laparoscopies had detectable PL mKRAS, suggesting that standard staging may be inadequate. Longer follow-up will elucidate utility of this promising molecular assay.Copyright © 2021 American College of Surgeons. Published by Elsevier Inc. All rights reserved.

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