Effect of ramucirumab plus paclitaxel in advanced gastric cancer according to the status of programmed cell death-ligand 1 (PD-L1) expression

Background: Ramucirumab, an anti-vascular endothelial growth factor receptor (VEGFR) monoclonal antibody (mAb), inhibits angiogenesis and reduces tumor activity. Programmed cell death-ligand 1 (PD-L1) might act upon VEGFR2 to induce cancer cell angiogenesis and metastasis. Herein, we investigated the efficacy of combining ramucirumab and paclitaxel according to the status of PD-L1 expression in patients with advanced gastric cancer (AGC). Methods: This analysis included AGC patients who received ramucirumab plus paclitaxel as 2^nd line therapy between December 1, 2018, and February 28, 2022, at Samsung Medical Center. All patient data analyses included an evaluation of PD-L1 expression using the combined positive score (CPS). We analyzed the efficacy and the survival of patients according to their PD-L1 expression. Results: We included 117 patients in this analysis, and 80 patients (68.4%) had a PD-L1 CPS of one or more, 37 (31.6%) had five or more, and 19 (16.2%) had ten or more scores. Progression-free survival (PFS) and overall survival (OS) did not differ significantly between patients with a PD-L1 CPS of less than one and one or more {PD-L1 <1% vs. PD-L1 ≥1%; PFS: median 3.6 months [95% confidence interval (CI): 2.4–4.8 months] vs. median 4.1 months (95% CI: 3.5–4.7 months), P=0.93; PD-L1 <1% vs. PD-L1 ≥1%; OS: median 7.0 months (95% CI: 5.4–8.6 months) vs. median 8.1 months (95% CI: 6.4–9.8 months), P=0.32}. PFS and OS did not differ significantly between patients with a PD-L1 CPS of less than 5 and 5 or more [PD-L1 <5% vs. PD-L1 ≥5%; PFS: 3.9 months (95% CI: 3.3–4.5 months) vs. 4.4 months (95% CI: 3.0–5.8 months), P=0.57; OS: 7.4 months (95% CI: 6.5–8.3 months) vs. 10.0 months (95% CI: 1.1–18.9 months), P=0.07]. Interestingly, with a PD-L1 CPS cutoff of 10, PFS and OS did differ significantly [PD-L1 <10% vs. PD-L1 ≥10%; PFS: 3.8 months (95% CI: 3.3–4.3 months) vs. 5.7 months (95% CI: 4.1–7.3 months), P=0.05; OS: 7.2 months (95% CI: 6.5–7.9 months) vs. 18.9 months (95% CI: 6.5–31.3 months), P=0.04]. Conclusions: No biomarkers have been established to predict survival times after ramucirumab plus paclitaxel treatment. This analysis suggests that a PD-L1 CPS cutoff of 10 might be novel a biomarker to predict the survival of AGC patients treated with ramucirumab and paclitaxel.