This study has focused on two factors, NLR and PNI, which can reflect the systemic inflammatory responses and nutritional status of GC patients, respectively. Generally, these two factors can also be used in the prognosis of gastric cancer. Previous studies have shown that NLR and PNI can be used in cancer prognoses (20–24). Since its introduction, NLR has received much attention as a new indicator of systemic inflammation, especially in the prognoses of malignant tumors (25, 26). Some previous studies have been conducted based on large sample sizes, but studies on gastric cancer need to be further carried out. As one of the indicators that can better reflect the nutritional status of cancer patients, PNI can be used in the prognosis of gastric cancer, which has been recognized in some studies (27, 28). This study aims to further compare and explore the performance of both factors in the prognostic evaluation of gastric cancer based on a large number of data, which is rarely investigated in previous studies. Ultimately, it was concluded in this study that although both PNI and NLR can reflect the prognosis of gastric cancer, PNI can be used as an independent prognostic factor for overall survival of GC patients, while NLR can not be used as such a factor.
Systemic inflammatory responses can promote tumor proliferation, angiogenesis, and tumor cell migration among cancer patients. They are closely related to tumorigenesis and tumor progression and an essential factor of the microenvironment of tumor cells (29). Inflammatory cells are involved in cell proliferation, invasion, migration, angiogenesis, and tumor metastasis. At the same time, tumors may be caused by recruited inflammatory cells, chemokines, and cytokines at sites of inflammation. In addition, inflammatory responses can further promote the progression of tumors. Inflammatory responses can lead to leukocytosis, neutrophilia, thrombocytosis, and lymphocytopenia (30). Platelets can act as reservoirs for the secretion of multiple growth factors that can further increase angiogenesis, tumor growth and metastases (31). Neutrophils may be involved in inflammatory responses through the releases of reactive oxygen species or nitric oxides and the remodeling of extracellular matrices (32). Lymphocytes are involved in inflammatory responses by inhibiting tumor proliferation and inducing anti-tumor activities causing cytotoxic cell death (33). Previous studies have also shown that WBC count can play an independent role in the prognoses of certain tumors. In addition, poor preoperative nutritional status is a common symptom among cancer patients, which is most visibly reflected by decreased serum albumin levels.
Albumin is the most abundant protein in plasma, which is often used in clinical practice to assess the nutritional status of patients. Hypoalbuminemia indicates poor nutritional status, which in turn leads to decreased immune functions among cancer patients and increases the risks of postoperative complications and tumor progression (34). Moreover, some previous studies have shown that systemic inflammation can lead to decreased albumin concentrations and hypoalbuminemia can also reflect increased systemic inflammatory responses (35, 36). PNI is determined on the basis of albumin concentration and lymphocyte count. Therefore, it is commonly regarded as one indicator of nutritional status. Meanwhile, it can also reflect inflammation levels of patients in some way. In previous reports, PNI has been regarded as a marker of systemic inflammation associated with cancer (37). Possibly due to this particular “dual status”, PNI has been used as an independent prognostic factor for many cancers. Under such a circumstance, an interesting question arises that whether PNI or NLR can be regarded as a more representative factor in the postoperative prognosis of gastric cancer. Experimental results in this study show that although both PNI and NLR can reflect the prognosis of gastric cancer, PNI is a better indicator reflecting overall survival of GC patients than NLR. During recent years, many studies have been conducted to investigate the roles of NLR in the prognoses of various cancers. However, there are relatively few studies on the role of NLR in the prognosis of gastric cancer. In addition, we have found that these studies mostly draw the conclusion that NLR could be used as an independent prognostic factor for gastric cancer. However, an opposite conclusion has been reached in some other studies. For example, Han et al. argued that NLR can not be used as an independent prognostic factor for gastric cancer (38). Zhu et al. argued that NLR can not be used to predict preoperative lymph node metastases or prognoses of patients with early gastric cancer (39). This indicates that more studies should be performed to investigate the roles of both NLR and PNI in the prognoses of different cancers. In this study, we have validated the predictive roles of these two factors in the prognosis of gastric cancer and reached the conclusion that is described above. However, this study is a retrospective study based on a small size of single-source samples. In the future, prospective studies should be carried out based on large sizes of multi-source samples.