Molecular diagnosis for detecting KRAS mutation in peritoneal washing fluid of pancreatic ductal adenocarcinoma

Positive peritoneal washing cytology is an indicator of poor prognosis in patients with pancreatic ductal adenocarcinoma (PDAC); however, its sensitivity is relatively low. This study evaluated the performance of peptide nucleic acid (PNA)-directed PCR clamping as a molecular-based peritoneal washing cytology for sensitive detection of KRAS mutation in PDAC. Intraoperative peritoneal washing fluid (IPWF) obtained from patients with PDAC who underwent surgery was analyzed. PNA-directed PCR clamping was performed on DNA extracted from IPWF. Among 54 patients enrolled, threshold cycle (Ct) was significantly lower in patients with positive peritoneal washing cytology than in those with negative peritoneal washing cytology (P < 0.001) and in patients with peritoneal dissemination than in those without peritoneal dissemination (P < 0.01). The optimal Ct cut-off to predict KRAS mutations in IPWF was 36.42 based on a receiver operating characteristic curve. The sensitivity, specificity, and accuracy for molecular diagnosis were 100%, 80.0%, and 85.2%, respectively. Peritoneal dissemination recurrence was significantly more frequent in patients with a positive molecular diagnosis than in those with a negative diagnosis (38.9 vs. 8.0%, P = 0.013). The genomic approach might be clinically valuable for a more precise tumor cell detection in IPWF.