Molecular Cytology by One-Step Nucleic Acid Amplification (OSNA) Assay of Peritoneal Washings during D2 Gastrectomy in Advanced Gastric Cancer Patients: Preliminary Results

The presence of peritoneal free cancer cells (FCC) in gastric cancer (GC) patients is a poor prognostic factor. D2 gastrectomy may induce exfoliated FCC spread from the primary tumour or involved lymph nodes (LN). Conventional cytology for FCC detection has several limitations, whereas prophylactic use of extensive intraoperative peritoneal lavage (IPL) does not improve survival. A prospective single-arm observational study was conducted to verify whether D2 gastrectomy causes an intraoperative increase of FCC in peritoneal fluid. Twenty-seven GC patients underwent D2 gastrectomy, followed by objective quantitative measurements of CK19 mRNA level reflecting FCC with One-Step Nucleic Acid Amplification (OSNA) assay. The IPL with 3000 mL of saline was performed twice: (1) after gastrectomy with D2 lymphadenectomy and (2) after alimentary tract reconstruction. The IPL samples were analysed by initial cytology and four (1–4) consecutive OSNA assays. Initial OSNA measurement (1) revealed positive results (≥24.6 cCP/μL) in 7 (29.6%) patients. Subsequent OSNA measurements showed a significant decrease in the FCC level after D2 gastrectomy (1 vs. 2; p = 0.0012). The first IPL induced a non-significant increase in the FCCs (2 vs. 3, p = 0.3300), but the second IPL reversed it to normal levels (3 vs. 4, p = 0.0.0574). The OSNA assay indicates a temporal intraoperative increase in the peritoneal FCC in advanced GC patients undergoing D2 gastrectomy. Two consecutive IPLs are necessary to reverse the increase of CK19 mRNA level in peritoneal washings.

Issues on peritoneal metastasis of gastric cancer: an update

Background Peritoneal metastasis (PM) is one of the most common forms of metastasis with a very poor prognosis in patients with gastric cancer (GC). The mechanisms, diagnosis, and management of PM remain controversial. Main body Stephen Paget’s “seed-and-soil” hypothesis gives us an illustration of the mechanisms of PM. Recently, hematogenous metastasis and exosomes from GC are identified as novel mechanisms for PM. Diagnostic accuracy of conventional imaging modalities for PM is not satisfactory, but texture analysis may be a useful adjunct for the prediction of PM. Biological markers in peritoneal washings are helpful in identifying patients at high risk of PM, but many limitations remain to be overcome. Response of PM from systemic chemotherapy alone is very limited. However, conversion therapy is confirmed to be safe and able to prolong the survival of GC patients with PM. As an important part of conversion therapy, intraperitoneal chemotherapy with taxanes has become an ideal approach with several advantages. Additionally, gastrectomy should be considered in patients who would tolerate surgery if a remarkable response to chemotherapy was observed. Conclusion Texture analysis is a reliable adjunct for the prediction of PM, and conversion therapy provides a new choice for GC patients with PM. The underlying mechanisms and new biological markers for GC patients with PM should be the direction of future studies. Furthermore, significant aspects of conversion therapy, such as timing and method of the operation, and the indications remain to be clarified.

CYTOLOGICAL DIAGNOSTICS OF INTRAOPERATIVE PERITONEAL WASHES IN GASTRIC CANCER

Diagnosis of peritoneal microcanceromatosis is the most important task allowing to determine treatment strategy for patients with stomach cancer. Laparoscopy combined with peritoneal flushing and subsequent cytological examination should be performed to detect the peritoneal microcanceromatosis at the preoperative stage. The objective of this work was to improve cytological diagnostics of peritoneal washings using immunocytochemical techniques and the cell block method. The work was carried out on the basis of 276 surgical peritoneal washings in patients with stomach cancer who were on treatment in the department of high-tech surgery of the Moscow Clinical Scientific Centre of the State Budgetary Healthcare Institution named after Loginov A.S. from June 2016 to June 2018. As a result, the optimal panel of monoclonal antibodies (Ber-EP4, CEA, CK20) was chosen, which increased the sensitivity from 52% to 96% and the specificity of cytological diagnosis from 80% to 98%, and the overall accuracy of the method from 67% to 98%.