Clinical outcomes of immune checkpoint inhibitor therapy for advanced lung adenosquamous carcinoma.

Background: Primary adenosquamous carcinoma (ASC) of the lung is a rare and aggressive disease and limited information is available on the efficacy of immune checkpoint inhibitors (ICIs) for this disease. Here, we evaluated the expression status of programmed death-1 ligand 1 (PD-L1) and efficacy of ICIs in patients with pulmonary ASC. Methods: The efficacy and toxicity of ICIs were examined in 38 patients with previously treated lung ASC from November 2017 to October 2021 in Zhejiang Cancer Hospital (Hangzhou, China). Survival curves were plotted using the Kaplan-Meier method and the Cox proportional hazards model applied for univariate and multivariate analyses. Results: A total of 38 patients with ASC were included in this retrospective study. ICI treatment induced an objective response rate (ORR) of 23.7% and a disease control rate (DCR) of 86.8%. The median progression-free survival (PFS) and median overall survival (OS) were 5.47 and 24.10 months, respectively. Seventeen patients were successfully evaluated for PD-L1 expression status, with 11 (64.7%) identified as PD-L1-positive. ORR and DCR for PD-L1-positive patients were 36.4% (4/11) and 100% (11/11) and the corresponding values for PD-L1-negative patients were 0 (0/6) and 50% (3/6), respectively. The median PFS of PD-L1-positive and PD-L1-negative patient groups was 5.00 and 1.90 months (P=0.166) while the median OS was 11.30 months and not reached, respectively (P=0.966). The incidence rate of immune-related adverse events (irAEs) was 52.6%, with 13.2% grade 3-4 irAEs. The most common irAEs were malaise and pneumonitis. One patient died of pneumonitis during the study. Conclusions: ICIs show considerable potential as a treatment option for lung ASC. PFS and OS rates are similar for PD-L1-positive and PD-L1-negative patients. Further large-scale studies are required to establish the relationship between PD-L1 expression and response to ICIs in ASC.