The impact of combined PD-L1 positive score on clinical response to nivolumab in patients with advanced esophageal squamous cell carcinoma

Background Nivolumab is recommended for patients with advanced esophageal squamous cell carcinoma (aESCC) refractory or intolerant to fluoropyrimidine-and platinum-based chemotherapy regardless of the tumor proportion score (TPS). However, the role of combined positive score (CPS) in predicting nivolumab efficacy remains unclear. We aimed to study whether TPS or CPS is a more suitable biomarker for predicting nivolumab efficacy in these patients. Methods We retrospectively collected data from patients with aESCC treated with fluoropyrimidines and platinum and subsequently received nivolumab monotherapy between January 1, 2014 and September 15, 2020. Next, we evaluated the efficiencies of TPS and CPS in predicting the clinical response to nivolumab using PD-L1 IHC 22C3 pharmDx assay. Results This study included 50 patients (CPS groups: >= 10/1-10/ < 1, n = 24/18/8, respectively; TPS groups, >= 10%/1%- 10%/ < 1%, n= 17/8/25, respectively). The median progression-free survival was 3.2, 2.5, and 1.5 months in the >= 10, 1-10 [hazard ratio (HR) vs. CPS of >= 10 group, 1.01; p = 0.98; adjusted HR, 1.33; p = 0.56], and < 1 CPS groups (HR vs. CPS of > 10 group, 3.44; p = 0.006; adjusted HR, 1.67; p = 0.41), respectively. For the patients with CPS of >= 10/1-10/ < 1 and TPS of >= 10%/1%-10%/ < 1%, the objective response rate was 30%/25%/0% and 36%/0%/19% and the disease control rate was 60%/50%/12% (p = 0.06) and 65%/40%/38% (p = 0.30), respectively. Conclusions This study suggests that a CPS of < 1 is not a strong predictor of efficacy but can predict the absence of response to nivolumab in patients with aESCC.