Intraoperative flow cytometry in detecting free carcinoma cells in peritoneal lavage fluid of gastric carcinoma cases

The free carcinoma cells (FCC) in peritoneal lavage fluid are an independent adverse prognostic factor in patients with gastric carcinoma. Detection of FCC in the pre-operative peritoneal lavage fluid is critical, as patients with FCC do not have a survival advantage with curative cytoreductive (CCR) surgery. Cytology is currently used to assess FCC, but its sensitivity is poor and there is a need for better sensitive techniques. We attempted to study the efficiency of intra-operative flow cytometry (FCM) in detecting FCC in peritoneal lavage fluid of gastric carcinoma patients. In this prospective study, 32 peritoneal lavage fluids were analyzed intra-operatively by cytology and FCM. The median time taken for sample processing was 47 min. The concordance was achieved in 84% (27/32) of samples. FCM detected FCC in 17 peritoneal lavage fluids, of which only 12 were reported positive by cytology. Five cases that had a FCC burden of less than 0.01% were reported negative by cytology. FCC with programmed death-ligand 1 (PD-L1) expression of greater than 50% was noted in 12 cases. Intra-operative FCM improves the detection of FCC in peritoneal lavage fluid compared to cytology. Due to higher sensitivity, flow cytometry offers a promising adjuvant to cytology and helps in deciding on judicious radical CCR.