Preoperative systemic immune-inflammation index for predicting the prognosis of thymoma with radical resection

Abstract

Background: To investigate the clinical significance of preoperative systemic immune-inflammation index (SII) in patients with thymoma who underwent radical resection.

Methods: This retrospective study involved 425 patients with thymoma who underwent radical resection at the First Affiliated Hospital of Nanjing Medical University between September 1, 2008 and December 30, 2019. Data regarding routine preoperative blood tests and clinical features were collected to calculate and analyze the SII, platelet-to-lymphocyte ratio (PLR), and neutrophil-to-lymphocyte ratio (NLR).

Results: Univariate analysis indicated that age (p = 0.021), tumor size (p = 0.003), extended resection (p < 0.001), Masaoka-Koga stage (p < 0.001), PLR (p = 0.012), NLR (p = 0.041), and SII (p = 0.003) were related to patient prognosis. A higher SII (>345.83) was a significant independent prognostic factor in this cohort (p = 0.001, HR = 5.756, 95% CI: 2.144-15.457). Multivariate analysis showed that a high PLR was significantly associated with overall survival (OS) (p = 0.008, HR = 3.29, 95% CI: 1.371-7.896), while a high NLR was a significant independent prognostic factor for shorter OS (p = 0.024, HR = 2.654, 95% CI: 1.138-6.19). SII had an area under the curve (AUC) of 70.6% (AUC = 0.706) exceeding the predictive value for PLR (AUC = 0.678) and NLR (AUC = 0.654).

Conclusion: Preoperative SII can predict the prognosis of thymoma patients who have undergone radical resection but further multicenter prospective studies are needed to investigate the role of SII in thymoma.

Keywords: NLR; PLR; SII; prognosis; thymoma.

FIGURE 1

Flow chart. PLR, platelet‐to‐lymphocyte ratio; NLR, neutrophil‐to‐lymphocyte ratio; SII, systemic immune‐inflammation index.

FIGURE 2

Overall survival (OS). The 5‐year OS rate was 94.0% and the 10‐year OS rate was 89.2%.

FIGURE 3

Kaplan–Meier overall survival (OS) analysis. (a) Kaplan–Meier OS analysis of gender (p = 0.321). (b) Kaplan–Meier OS analysis of age (p = 0.016). (c) Kaplan–Meier OS analysis of WHO type (p = 0.174). (d) Kaplan–Meier OS analysis of tumor size (p = 0.001). (e) Kaplan–Meier OS analysis of myasthenia (p = 0.122). (f) Kaplan–Meier OS analysis of extended resection (p < 0.001). (g) Kaplan–Meier OS analysis of Masaoka‐Koga stage (p < 0.001). (h) Kaplan–Meier OS analysis of PLR (p = 0.008). (i) Kaplan–Meier OS analysis of NLR (p = 0.035). (j) Kaplan–Meier OS analysis of SII (p = 0.001).

FIGURE 4

Correlation analysis and selection of predictors. Platelet‐to‐lymphocyte ratio (PLR), neutrophil‐to‐lymphocyte ratio (NLR) and systemic immune‐inflammation index (SII) were strongly correlated. The Masaoka‐Koga stage and the World Health Organization (WHO) histological classification had a weak but significant correlation (r = 0.226 and p < 0.001). WHO histological classification and extended resection had a weak but significant correlation (r = 0.153 and p = 0.002).

FIGURE 5

Receiver operating characteristic (ROC) curve. Systemic immune‐inflammation index (SII) had an area under the curve (AUC) of 70.6% (AUC = 0.706), thus exceeding the predictive value for platelet‐to‐lymphocyte ratio (PLR) (AUC = 0.678) and neutrophil‐to‐lymphocyte ratio (NLR) (AUC = 0.654).