Programmed death-1 and PD-1 ligand-1 expression in early onset gastric carcinoma and correlation with clinicopathological characteristics.

Purpose: Early onset gastric carcinoma (EOGC) is thought to be developed by a distinct molecular genetic profile of gastric carcinoma occurring at an older age. The aim of this study was to compare clinicopathological features and expression patterns of programmed death-1 (PD-1) and its ligand PD-L1 in young and older GC patients. Methods: Consecutive cases of GC presented to our hospital between 2007-2016 were collected. Clinicopathological features and overall survival data of EOGC patients (initially diagnosed at 40 years old or younger) were retrospectively reviewed from hospital records and compared with data of GC in the elderly (GC-E) (age ≥60 years). We investigated expression of PD-1 and PD-L1 by immunohistochemistry in both GC groups. Staining results were correlated with clinicopathological characteristics and overall survival. We then compared expression of PD-1 and PD-L1 with EOGC and GC-E. Results: Two thousands one hundred and forty five GC cases were collected. All 109 EOGC cases and 116 randomly selected GC-E cases were enrolled in the current study. Compared to GC-E patients, EOGC had a significantly higher proportion of female and gastric body location, a larger diameter, a higher proportion of low adhesive adenocarcinoma or diffuse gastric carcinoma, and a higher proportion of poorly differentiated tumors. PD-L1 was positively expressed in tumor cells in 43.6% (98/225) of GC cases and was weak to medium positive in most positive cases. The intensity of PD-L1 expression in tumor cells was significantly higher in EOGC (P=0.02). The positive rate of PD-L1 expression in tumor cells was significantly higher in EOGC than in GC-E (P=0.02). Conclusion: Clinicopathological characteristics of EOGC were distinctive from GC-E patients. EOGC had poorer prognosis compared to the older age group. Expression of PD-L1 in EOGC was significantly higher than in GC-E.