Background: Immune checkpoint inhibitors (ICIs) have become the standard of care for the treatment of patients with driver mutation absent advanced non-small cell lung cancer (NSCLC). The present study aimed to develop a reliable, reproducible, and practical scoring system to prognosticate and predict response to ICI response in patients with advanced NSCLC.Patients and methods: All patients who were diagnosed as having unresectable/advanced stage NSCLC and were treated with at least one cycle of ICIs at the Medical Oncology Departments of Dr. Burhan Nalbantoglu State Hospital (Nicosia, Cyprus) and Near East University Hospital (Nicosia, Cyprus) were included in the study. The association between variables and OS was evaluated using a Cox proportional hazards regression model. Variables with a P-value less than 0.05 in the univariate analysis were included in the multivariate model. A prognostic scoring system was developed. Survival estimates were calculated using the Kaplan -Meier method. The value of the Concordance index (C-index) and the area under the curve (AUC) was used to evaluate the discriminative ability of scoring systems. Results: One hundred fifty consecutive patients with unresectable/metastatic NSCLC who received PD-1 inhibitors between March 2017 and November 2022 were included. In the multivariate Cox regression model, serum lactate dehydrogenase (LDH), C-reactive protein (CRP) levels, and Eastern Cooperative Oncology Group Performance Status (ECOG PS) were significantly associated with OS. We generated a new score using CRP 31.0 mg/dL, ECOG PS 32, and LDH level >ULN. Relative weight was based on the HRs of multivariate analyses (CRP 31.0 mg/dL 2 points, ECOG PS 32 2.5 points, and LDH level >ULN 1.5 points). The cohort was divided into three risk groups based on the sum of factors present: 0-2.5 (good risk), 3.5-4.5 (intermediate risk), or 6 (poor risk). The median OS was 18.9, 7.4, and 2.9 months for good, intermediate, and poor risk categories, respectively (log-rank test, p<0.001). The Harrell C-index of CEL to predict OS and PFS was 0.73 and 0.69, respectively, indicating significant predictability. The AUC of the scoring index for predicting the responses was 0.765 (95% CI: 0.685-0.845). Conclusion: The CEL score is a promising prognostic and predictive index consisting of serum CRP levels (C), ECOG PS (E), and serum LDH levels (L). This represents another step forward in the treatment of patients with advanced NSCLC.
