Relationship Between Programmed Death Receptor-Ligand 1 Expression and Response to Checkpoint Inhibitor Immunotherapy in Pulmonary Sarcomatoid Carcinoma: A Pooled Analysis

Background: Pulmonary sarcomatoid carcinoma (PSC) or pleomorphic carcinoma is a rare subtype of non-small cell lung cancer. Some reports have suggested the efficacy of checkpoint inhibitor immunotherapy for PSC. However, owing to the small number of patients in each report, it remains unclear whether programmed death receptor-ligand 1 (PD-L1) expression is predictive of tumor response or survival. Patients and Methods: The English literature was systematically searched for articles published from 2015 to 2019 and reported on tumor response or progression-free survival (PFS) after immunotherapy for advanced PSC. In addition, our institutional electronic medical records were searched for eligible cases to be included. Pooled analyses were performed. Results: Analyses included 90 patients. Best tumor response was partial or complete response in 54.5%, stable disease 15.9%, and progressive disease in 29.6%. The median PFS was 7.0 months. Among 66 patients with reported PD-L1 expression, the level was <1% in 7 patients (10.6%), 1%-49% in 10 patients (15.2%), and ≥50% in 49 patients (74.2%). A positive relationship between PD-L1 level and tumor response was observed. Among 47 patients with a PD-L1 of ≥50%, 33 patients (70.2%) achieved response, compared with 5 of 10 patients (50%) with a PD-L1 of 1%-49% and 2 of 7 patients (28.6%) with a PD-L1 of <1% (P =.026). PFS was superior among patients with a PD-L1 of ≥1% compared with those with a PD-L1 of <1% (14.4 months vs. 2.7 months respectively; P =.04). Conclusions: Among patients with advanced PSC, PD-L1 expression is significantly associated with increased tumor responses and improved PFS after checkpoint inhibitor immunotherapy.