Abstract 116P
Background
In recent years, radiotherapy, chemotherapy or targeted therapy have made limited progress in advanced gastric cancer (GC), new and effective treatments are needed. Immune checkpoint inhibitors targeting programmed death-1/ligand-1 have been a novel treatment option, PD-L1 and microsatellite instability (MSI) status have been investigated as biomarkers to predict treatment efficiency in some cancer types. As PD-L1 expression on tumor cells and tumor-infiltrating immune cells shows distinct roles in regulating anticancer immunity, our study provided insights into PD-L1 expression on both cell types, as well as microsatellite instability status in Chinese GC populations.
Methods
Gastric tumor samples collected in China between January 01, 2017 and April 15, 2020 were analyzed by a College of American Pathologists-certified and Clinical Laboratory Improvement Amendments-accredited lab. MSI status was measured by targeted next-generation sequencing covering 500 MSI loci. IHC staining for PD-L1 expression was performed using SP263 or 22C3. We scored percentage of PD-L1 expression on tumor cells as TPS: TC3≥50%, TC2≥5% and <50%, TC1≥1% and <5%, and TC0<1%; Similarly, we scored percentage of PD-L1 expression on infiltrating immune cells as IPS: IC3≥10%, IC2≥5% and <10%, IC1≥1% and <5%, and IC0<1%.
Results
540 GC patients’ tumor samples were analyzed. 10 (1.8%) individuals had tumors cells PD-L1 scores as TC3, 49 (9.1%) as TC2, 80 (14.8%) as TC1 and 401 (74.3%) as TC0. Meanwhile, infiltrating immune cells PD-L1 scores of patients were 22 (4.1%) for IC3, 26 (4.8%) for IC2, 24 (4.4%) for IC1 and 468 (86.7%) for IC0, respectively. 27 (5.0%) of patients were simultaneously TC1/2/3 and IC1/2/3. 27 (5.0%) patients were MSI-H, 13 (48.1%) of MSI-H GC patients were TC1/2/3, and 4 (14.8%) of MSI-H GC patients were IC1/2/3. In addition, TC1/2/3 showed an association with MSI-H (P=0.0057), while IC1/2/3 was not associated with MSI-H (P=0.793).
Conclusions
The PD-L1 expression profile on tumor cells and tumor-infiltrating immune cells and MSI status of Chinese gastric cancer patients in this study will further assist the utilization of them as predictive biomarkers in clinical practice.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.