Association Between Systemic Immune-Inflammatory Index (SII) and Cancer Grading and Staging: Evidence from the Current Scientific Literature

Background: Accumulating evidence demonstrates that inflammatory responses play a critical role in tumor progression, invasion, and metastasis. In recent years, systemic immune-inflammatory (SII) markers have emerged as valuable tools for evaluating tumor grade and prognosis in solid tumors. To assess SII scores associated with neoplasm-related grading and staging in order to investigate the incidence rate in SII levels and cancer-related aggressiveness. Methods: The present review was recorded in Figshare system with id no. 10.6084/m9.figshare.31029121. Observational studies recording grading and staging differences (advanced III–IV vs. early 0–II) in SII values among cancer patients were included in the present review. Frequencies were collected among cancer patients, along with low and high SII levels and related grading and staging scores. Results: A total of ten studies were included in the present review. Considering cancer grading classification and SII levels, our data showed significant associations not recorded in all the selected studies. Additionally, high SII values appeared to be significantly associated with advanced-stage cancer (stages III–IV), while lower SII values were associated with an increased probability of early-stage tumors (stages 0–II), (p < 0.05). Conclusions: The SII marker has shown potential predictive value in cancer. However, the SII is a relatively novel index in which a direct causal effect on tumor initiation or subsequent disease progression remains to be comprehensively investigated.