There is growing evidence that the SII and PNI, which reflect systemic inflammation and nutritional status, can reflect the relationship between host inflammation and immune status, and accurately predict the prognosis of cancer patients[26]. However, the relationship between the PNI, SII and clinical outcomes in CRC patients remains unclear. The primary objective of this study was to assess the prognostic value of the SII and PNI in CRC patients undergoing surgical removal. Our results show that among the risk factors associated with five-year survival or death in CRC patients, the PIN and SII are closely associated with mortality in CRC patients. Survival analysis revealed that CEA, tumor stage, pathological type, postoperative complications and PNI were significant risk factors for CRC patients, with PNI showing the highest significance.
The nutritional and inflammatory status of the body has been shown to play an important role in the occurrence, development and prognosis of tumors. Previous studies have confirmed that preoperative hypoalbuminemia is closely related to postoperative morbidity and mortality, as well as a poor survival rate after tumor surgery[27]. Serum albumin levels are important independent biomarkers for a wide range of human diseases, including cancer[28]. Interestingly, albumin has been shown to display active tumor targeting effects through its interactions with GP60 and secreted protein acidic and rich in cysteine in tumor-associated endothelial cells and the tumor microenvironment[29].
The prognostic value of a pretreatment PNI in patients with lung cancer was systematically evaluated in a 2018 meta-analysis. A low pretreatment PNI was found to be closely associated with poor OS in lung cancer patients, and a predictor of poor survival[30]. Similarly, Zhang et al. examined the relationship between the PNI and OS, disease free survival and progression free survival (PFS) in breast cancer patients receiving clinical treatment. High PNI values were found to be a favorable independent predictor of prolonged OS and PFS in breast cancer patients after clinical treatment, and the PNI was significantly correlated with the prognosis of breast cancer patients[31].
A study evaluating the relationship between preoperative SII and the prognosis and clinicopathological features of bladder cancer in 7087 patients found that preoperative SII elevation was associated with poor tumor differentiation, high tumor stage, lymph node involvement, and tumor size ≥ 3 cm. Moreover, preoperative SII elevation was significantly associated with poor survival outcomes and adverse pathological features[32]. The SII, as an inflammatory indicator, has been identified as a prognostic biomarker in various diseases including acute kidney injury, fatty liver, hyperlipidemia, ischemic stroke, Alzheimer's disease and cerebral hemorrhage[33–37].
In recent years, increasing evidence has suggested that the interaction between tumor cells and platelets is a prerequisite for the successful transmission of blood metastasis[38]. Platelets stimulate the proliferation of cancer cells by releasing a variety of cytokines and chemokines, as well as accelerate tumor angiogenesis through various angiogenic regulatory factors, thereby playing a crucial role in the growth and metastasis of cancer cells[39]. Zhang et al. demonstrated that cancer cells can be reprogrammed to a metastatic state by acquiring platelet mitochondria via the PINK1/Parkin-Mfn2 signaling pathway. In addition, platelet mitochondria regulate the GSH/GSSG ratio and reactive oxygen species of tumor cells, promoting lung metastasis of osteosarcoma[40]. Neutrophils are the most abundant myeloid cells in human blood and are important regulators of cancer[41]. External stimulation of the tumor microenvironment can trigger the accumulation of tumor-associated neutrophils in local areas and switch between anti-tumor and pro-tumor phenotypes[42]. Anti-tumor neutrophils kill tumor cells directly through cytotoxic effects, as well as indirectly through the activation of adaptive immune responses. In contrast, the pro-tumor phenotype of neutrophils may be related to cell proliferation, angiogenesis, and immunosuppression in the tumor microenvironment[43].
There are several limitations associated with the analytical process of this retrospective study. First, subjectivity in the collection of CRC patient data may have contributed to biases in our findings. Secondly, the influencing factors included in our study are not comprehensive. Third, this retrospective study is a single-center study that includes a relatively small number of patients, which may affect the accuracy of our results. Future studies that incorporate more patients from multiple centers and a comprehensive risk factor analysis are the next step to carry out survival and related risk factor analyses of CRC patients to better serve clinicians and patients.