Utility of molecular analysis of peritoneal fluid in staging laparoscopy of advanced oesophagogastric junction and gastric cancer prior to neoadjuvant treatment

Abstract The significance of molecular analysis of peritoneal fluid in staging laparoscopy of oesophagogastric junction (EGJ) and gastric cancer is still controversial. METHODS: A retrospective analysis of prospective data collection of all patients diagnosed with locally advanced gastric neoplasia or Siewert II-III EGJ cancer from July 2009 to October 2019 who underwent staging peritoneal lavage prior to neoadjuvant treatment was performed. Cytology studies and molecular analysis of peritoneal lavage were performed by real-time reverse transcriptase polymerase chain reaction (RT_PCR) of carcinoembryonic antigen (CEA) and cytokeratin 20 (CK20) as tumor makers. RESULTS: 168 patients were operated. Citology and molecular analysis were performed in 138 patients. Macroscopic carcinomatosis (P+) was evidenced in 12.3% (17 patients). Of the remaining 87.7% (121 patients), 9.9% (12 patients) had positive cytology. In 21% (29 patients) disseminated macroscopic or microscopic disease (P + or Cyt+) was identified. 11.6% (16 patients) were P0Cyt- but RT-PCR+. Of these, 9 responded to chemotherapy before salvage surgery. The sensitivity of cytology and molecular analysis was 0.70 and 0.76, respectively (p = 0.67). The survival of Cyt-RT_PCR + vs. Cyt + RT_PCR + patients was similar (p = 0.1). However, there were no differences in the survival curves between Cyt-RT_PCR- patients vs Cyt-RT_PCR + patients who underwent salvage surgery (p = 0.69). CONCLUSION: Molecular analysis showed a sensitivity of 76%. In our study, the survival of P0 Cyt-RT_PCR + patients responding to chemotherapy and undergoing surgery was similar to that of P0 Cyt-RT_PCR- patients but less disease free survival.