Preoperative prognostic nutritional index level is associated with tumour-infiltrating lymphocyte status in patients with surgically resected lung squamous cell carcinoma

Abstract

OBJECTIVES: The prognostic nutritional index (PNI) is an indicator of systemic immune-nutritional condition and is a well-known prognostic biomarker in lung cancer patients. Tumour-infiltrating lymphocytes (TILs) is a specific histological feature of cancers, influencing an individual's immunological tumour responses. However, whether PNI can reflect lung cancer patients' prognosis through local immunity such as TIL is unclear. METHODS: We selected 64 lung squamous cell carcinoma patients who underwent curative operations. We investigated the significance of preoperative PNI level and evaluated the relationship between PNI and immune cells surrounding the lung cancer tissue using immunohistochemical analysis of a cluster of differentiation (CD)3, CD4, CD8 and CD68. RESULTS: A low-PNI level was significantly associated with a worse postoperative prognosis (P = 0.042). The PNI (hazard ratio 2.768, 95% confidence interval 1.320-5.957; P = 0.007) was an independent prognostic factor. The low-PNI group had a significantly shorter recurrence-free survival and overall survival (P = 0.013 and P = 0.002, log-rank test) compared with the high-PNI group. A significant positive correlation between PNI components including preoperative peripheral blood lymphocyte count and serum albumin concentration, and TILs, was observed. Absolute numbers of TILs in the preoperative high-PNI group were significantly increased compared with those in the preoperative low-PNI group (CD3+ cells; P = 0.002, CD4+ cells; P = 0.049 and CD8+ cells; P = 0.024). CONCLUSIONS: The preoperative PNI level was strongly associated with the postoperative outcome in lung cancer patients. Considering the positive relationship between preoperative PNI level and TIL status, preoperative immune-nutritional condition may influence lung cancer patients' postoperative prognosis through local immunity as well as systemic immune response.