Preoperative PD-1+CD4+ lymphocytes reflect immunological and physical frailty and are associated with postoperative infectious complications following gastrectomy for gastric cancer.

Postoperative infectious complications (PICs) are major adverse events following gastrectomy for gastric cancer. The present study investigated whether preoperative programmed cell death 1 (PD-1)+CD4+ lymphocytes reflect immunological and physical frailty and predict PICs. A total of 85 patients who underwent gastrectomy for gastric cancer were retrospectively enrolled. Blood samples were collected preoperatively, and PD-1+CD4+ cells were analyzed using flow cytometry. Patients were divided into PD-1high (N=43) and PD-1low (N=42) groups based on the median value of preoperative PD-1+CD4+/CD4+ cells (cutoff, 22.3%). Preoperative immune-inflammatory markers and nutritional indices included the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), C-reactive protein-to-albumin ratio (CAR), prognostic nutrition index (PNI) and controlling nutritional status (CONUT) score. Physical vulnerability was assessed using the fall risk assessment score (FRAS) and Charlson comorbidity index (CCI). The PD-1high group was older than the PD-1low group, with no significant differences in sex, comorbidities, or surgical and pathological factors. The PD-1high group had a significantly higher incidence of the PICs (42 vs. 19%; P<0.05). In addition, the PD-1high group exhibited higher C-reactive protein levels, and lower total lymphocyte counts and albumin levels compared with the PD-1low group (P<0.05, respectively). The two groups had significant differences in preoperative NLR, CAR, PNI, CONUT score and FRAS. Notably, there were significant associations between PD-1+CD4+/CD4+ cells and NLR, PLR, CONUT score, PNI, FRAS and CCI (all P<0.05). Preoperative PD-1+CD4+/CD4+ cells were significantly associated with increased PIC risk and markers of immunological and physical frailty. This biomarker may be useful for identifying vulnerable patients requiring tailored perioperative care.