[Frequency of MSI, PD-L1 (CPS), HER2 in poorly cohesive gastric carcinomas]

Gastric cancer (GC) is a heterogeneous tumor with various molecular changes. An active search for molecular markers is crucial to determine the effectiveness of drug treatment and prognosis of the disease. Several biomarkers have the greatest clinical significance: HER2, MSI / dMMR, PD-L1 (CPS), EBV and Claudin 18.

To study the frequency of HER2, MSI / dMMR and PD-L1 (CPS) in patients with operable GC depending on the tumor type according to P. Lauren.

The study included 600 patients with GC who underwent radical surgical treatment at the N.N. Blokhin National Medical Research Center of Oncology from 2018 to 2023.

In the study, the proportion of diffuse GC was 21.5% (120/600). HER2 overexpression was found in 5.2% (5/96) of cases with diffuse GC, 20.4% (37/181) of cases with intestinal GC, 10.1% (7/69) of cases with mixed GC (p=0.0029). The incidence of MSI was 3.3% (4/120) of cases with diffuse GC, 11.2% (28/251) of cases with intestinal GC, 7.3% (7/97) of cases with mixed GC (p=0.0378). PD-L1 expression (CPS> 1) was found in 42.3% (11/26) of cases with diffuse GC, 59.4% (35/59) of cases with intestinal GC, 27.3% (9/33) of cases with mixed GC (p=0.006). In poorly cohesive/signet ring cell cancer MSI occurred in 2.5% (2/79) of cases; HER2 overexpression - in 2.9% (2/68) of cases; PD-L1 (CPS> 1) - in 42.1% (8/19) of cases.

Our study demonstrated that in diffuse and poorly cohesive/signet ring cell GC the frequency of occurrence of the above clinically significant tumor biomarkers is lower compared to intestinal/mixed GC.