Molecular Peritoneal Staging for Pancreatic Ductal Adenocarcinoma Using Mutant KRAS Droplet-Digital Polymerase Chain Reaction: Results of a Prospective Clinical Trial

Abstract

BACKGROUND: Pancreatic 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 DESIGN: Patients 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. RESULTS: There 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. CONCLUSIONS: This 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.

Levels of tumor markers CEA/CA 19–9 in serum and peritoneal lavage predict postoperative recurrence in patients with pancreatic cancer

“…Recently, Yonkus et al demonstrated a significant association between pCEA/pCA 19–9 and positive abdominal metastatic findings, such as radiographically invisible hepatic or peritoneal metastasis in patients with PDAC. 18 However, the authors also concluded that the prognostic impact of pCEA/pCA 19–9 remains controversial. One strength of the present study is the association of pCA 19–9 with peritoneal recurrence, even in patients with HEP − PER−CY−, whereas patients with elevated levels of both pCA 19–9 and sCA 19–9 were found to be more likely to develop hepatic recurrence.…”

“…In patients with PDAC, recent advances in molecular biochemistry have also enabled the detection of minimal residual disease in the peritoneal lavage fluid with superior sensitivity to conventional cytology 16,17 . Even yet, tumor markers in peritoneal lavage fluid have been rarely evaluated, and their clinical utility remains controversial 18,19 …”

“… 16 , 17 Even yet, tumor markers in peritoneal lavage fluid have been rarely evaluated, and their clinical utility remains controversial. 18 , 19 …”

“…16,17 Even yet, tumor markers in peritoneal lavage fluid have been rarely evaluated, and their clinical utility remains controversial. 18,19 The present study aimed to determine the best molecular diagnostic approach using tumor markers to select the high risk of recurrence in patients with PDAC. We conducted tumor marker analyses using the serum and paired peritoneal lavages samples collected from the patients with PDAC undergoing surgery and evaluated their clinical relevance.…”

“…Taken together, pCA 19-9 and its combination with sCA19-9 or pCEA can be a powerful diagnostic tool to identify a subgroup of patients at high risk of recurrence, especially in CY− cases.Although several previous studies have suggested the use of peritoneal lavage CEA as a potential predictor of peritoneal recurrence and worse OS in patients with PDAC,[26][27][28][29] only a limited number of studies have focused on peritoneal lavage CA 19-9. Recently, Yonkus et al demonstrated a significant association between pCEA/ pCA 19-9 and positive abdominal metastatic findings, such as radiographically invisible hepatic or peritoneal metastasis in patients with PDAC 18. However, the authors also concluded that the prognostic impact of pCEA/pCA 19-9 remains controversial.…”