Pretreatment systemic inflammation response index (SIRI) is an independent predictor of survival in unresectable stage III non-small cell lung cancer treated with chemoradiotherapy: a two-center retrospective study.

Background: Circulating immune cells influence the efficacy of cancer therapy. This study aimed to investigate the prognostic values of different peripheral blood leukocyte (PBL) biomarkers in non-small lung cancer (NSCLC) patients treated with chemoradiotherapy.

Methods: An independent cohort of 176 stage III NSCLC patients who were diagnosed at Shanghai Pulmonary Hospital and Zhejiang Cancer Hospital between April, 2010, and September, 2018, and had available pretreatment peripheral blood tests was enrolled. The patients were all treated with concurrent or sequential chemoradiotherapy according to international clinical guidelines, with conventional fractionated radical radiotherapy. The receiver operating characteristic curve and the Youden index were used to determine the optional cutoff values of PBL biomarkers for distinguishing prognosis. Univariate and multivariate Cox proportional hazards regression analyses were performed to identify the factors significantly correlated with overall survival.

Results: The cohort had a median follow-up time of 21.7 (3.1-121) months. The 3- and 5-year OS rates of all patients were 34.7% and 27.5%, respectively. Univariate analysis showed that gender (P=0.011), smoking (P=0.011), tumor-node-metastasis (TNM) stage (P=0.002), pretreatment peripheral blood neutrophil-to-leukocyte ratio (P=0.013), and systemic inflammation response index (SIRI, P<0.001) were all correlated with OS in NSCLC patients. Moreover, multivariate analysis revealed that TNM stage (HR =1.541, 95% CI: 1.166-2.036, P=0.010) and SIRI (HR =1.868, 95% CI: 1.016-3.436, P=0.018) were significantly and independently associated with OS. However, the median OS of stage IIIB NSCLC patients with low SIRI (≤2.0) was longer than that of stage IIIA NSCLC patients with high SIRI (>2.0) (33.9±4.1 19.6±2.5 months).

Conclusions: Pretreatment peripheral blood SIRI was found to be a simple independent predictor of OS in stage III NSCLC patients who underwent chemoradiotherapy. As a novel prognostic marker, the prognostic value of the SIRI is superior to that of the NLR. Low SIRI could be a better prognostic stratification factor for NSCLC patients with different TNM stages.