Regimen Selection for Chemoimmunotherapy in Nonsquamous Non–Small Cell Lung Cancer with Low PD-L1 Expression: A Multicenter Retrospective Cohort Study

Background: Although chemoimmunotherapy is recommended for advanced nonsquamous non–small cell lung cancer (NSCLC) with low programmed cell death ligand 1 (PD-L1) expression, no head-to-head comparisons of immune checkpoint inhibitors (ICIs) have been performed. Therefore, we compared the effect and safety of regimens in these patients to guide evidence-based treatment. Methods: This retrospective study included patients with advanced nonsquamous NSCLC with a PD-L1 tumor proportion score of 1% to 49% administered ICI combination platinum-based chemotherapy between May 2018 and May 2023 at 19 institutions in Japan. The main analysis compared survival outcomes and the incidence of grade ≥3 adverse events among regimens. Results: Among 316 included patients (median [range] age, 69 [36–89] years; 242 males; 41 never smokers), 200 (63%), 68 (22%), and 48 (15%) received chemotherapy combined with anti-programmed cell death protein 1 (PD-1), anti-PD-L1, and anti-PD-1/cytotoxic T-lymphocyte associated protein 4 (CTLA-4) antibodies, respectively. The median overall survival times were 28.6, 23.1, and 24.4 months (P = .41), and the median progression-free survival times were 9.4, 7.2, and 8.7 months (P = .28) in the anti-PD-1/Chemo, anti-PD-L1/Chemo and anti-PD-1/CTLA-4/Chemo groups, respectively. The anti-PD-1/CTLA-4/Chemo group had the lowest incidence of hematologic toxicity (P = .13) and the highest incidence of nonhematologic toxicity (P = .07). The incidence of grade ≥3 pneumonitis was significantly lower in the anti-PD-L1/Chemo group (P = .049). Conclusions: Despite comparable survival benefits, adverse events differed among three regimens in patients with low PD-L1 expression. Notably, anti-PD-L1 antibody combination chemotherapy may reduce the risk of severe pneumonitis.