A genomically stable molecular type of gastric cancer as a predictor of peritoneal relapse after radical surgical treatment

Peritoneal metastases are commonly associated with gastric cancer (GC) recurrence after radical treatment. Thus, patients at a high risk of peritoneal relapse require adjuvant intraperitoneal chemotherapy during the initial treatment. Along with clinical and morphological predictors of peritoneal relapse, another approach in surgical oncology is proving to be promising today. It refers to the prediction of the risk of developing metachronous peritoneal metastases in various molecular types of GC. Objective — to study the risk of peritoneal relapse in patients with the genomically stable type of GC in comparison to its other molecular types. Materials and methods. 37 patients with GC were enrolled into the study and evaluated after the radical treatment. 19 (51.4 %) patients formed a subgroup with peritoneal relapse and 18 patients (48.6 %) were included into a subgroup without metachronous carcinomatosis in the long term. All patients underwent immunohistochemical study for the E‑cadherin (CDH1 gene) expression in a gastric tumor. The genomically stable molecular type was identified on the basis of the aberrant E‑cadherin (CDH1‑mutated) tumor phenotype detection. Results. There was a statistically significant difference (p = 0.022, χ2 = 5.22) in the degree of aberrant E‑cadherin expression in subgroups of patients with and without peritoneal relapse — 68.4 and 33.3 %, respectively. Hence, it was noted that the genomically stable molecular type had a significant influence on the risk of peritoneal recurrence: the 2‑year peritoneal relapse‑free survival of GC patients with E‑cadherin of aberrant type was 31.6 %, and in GC patients with wild‑type E‑cadherin expression — 71.4 % (p = 0.022). The 2‑year overall survival of GC patients with aberrant type E‑cadherin expression was 36.8 %, whereas in GC patients with E‑cadherin of the wild type — 77.8 % (p = 0.003). Conclusions. The study found that the genomically stable molecular type of GC may serve as a predictive factor associated with an increased probability of peritoneal relapse, as well as a prognostic factor due to its negative impact on patient prognosis. The genomically stable molecular type of GC may be used as a tool for forming a cohort of patients with indications for adjuvant intraperitoneal therapy.