Soluble interleukin-2 receptor as a predictive biomarker for poor efficacy of combination treatment with anti-PD-1/PD-L1 antibodies and chemotherapy in non-small cell lung cancer patients

Soluble interleukin-2 receptor (sIL-2R) suppresses effector T-cells. Few studies have assessed serum sIL-2R in patients receiving immunotherapy. We evaluated the association between serum sIL-2R levels and the efficacy of anti-programmed cell death 1/ programmed death-ligand 1 (anti-PD-1/PD-L1) antibody combined with chemotherapy in non-small cell lung cancer (NSCLC) patients. We prospectively enrolled NSCLC patients who received anti-PD-1/PD-L1 antibody combined with platinum-based chemotherapy between 8/2019 and 8/2020 and measured their serum sIL-2R. The patients were divided into high and low sIL-2R groups based on the median of sIL-2R levels at pretreatment. Progression-free survival (PFS) and overall survival (OS) of patients in the high and low sIL-2R groups were compared. The Kaplan–Meier curves of PFS and OS were evaluated using the log-rank test. The multivariate analysis of PFS and OS was performed using the Cox proportional hazard models. Among 54 patients (median age 65, range 34–84), 39 were male and 43 had non-squamous cell carcinoma. The sIL-2R cut-off value was 533 U/mL. Median PFS was 5.1 months (95% CI, 1.8–7.5 months) and 10.1 months (95% CI, 8.3-not reached [NR] months) in the high and low sIL-2R groups ( P = 0.007), respectively. Median OS was 10.3 months (95% CI, 4.0–NR months) and NR (95% CI, 10.3–NR months) in the high and low sIL-2R groups ( P = 0.005), respectively. Multivariate Cox regression analysis showed that high sIL-2R was significantly associated with shorter PFS and OS. SIL-2R may be a biomarker for the poor efficacy of anti-PD-1/PD-L1 antibody combined with chemotherapy.