AbstractBackgroundIt is still unclear whether patients with advanced non‐small cell lung cancer (NSCLC), with disease progression after initial immune checkpoint inhibitor (ICI) therapy, would benefit from ICIs readministration.Patients and MethodsWe retrospectively collected data from patients with advanced NSCLC who received ICI retreatment. Depending on the disease status at the discontinuation of the initial ICI therapy, the patients were divided into two groups: with disease progression (PD group) and without disease progression (Without PD group). Patients in the Without PD group were required to experience disease progression during the treatment‐free period. Efficacy was assessed by measuring the objective response rate (ORR) and progression‐free survival in retreatment (PFS‐R), while safety was assessed using the incidence of immune‐related adverse events (irAEs).Results30 (46.7%) of 64 eligible patients were included in the PD group and 34 (53.1%) in the Without PD group. Patients in the Without PD group had better clinical outcomes than those in the PD group (ORR, 29.4% vs. 6.7%;p= 0.03, median PFS‐R, 4.1 months vs. 2.2 months, hazard ratio [HR], 0.61; 95% confidence interval [CI], 0.36–1.04;p= 0.07). Multivariate Cox regression analysis showed that patients in the Without PD group had significantly longer PFS‐R than those in the PD group (HR 0.42, 95% CI, 0.21–0.85;p= 0.015). In terms of safety, 28.1% of patients observed irAEs during ICI retreatment, and the incidence rate of grade 3 or higher irAEs was 7.8%. Specifically, of the 28 patients who discontinued their initial ICI treatment because of irAEs, 35.7% developed irAEs, and 28.6% experienced relapsed irAEs during ICI retreatment.ConclusionImmune checkpoint inhibitor retreatment demonstrated efficacy in patients who discontinued initial ICI therapy for reasons other than disease progression. However, ICI retreatment was ineffective in patients with disease progression during the initial ICI treatment.