Correlation of combined positive score of PD-L1 expression and clinical efficacy for advanced esophageal squamous cell carcinoma treated with nivolumab monotherapy.

Abstract

289 Background: Based on the results of the ATTRACTION-3 trial, nivolumab has shown superiority compared to taxane monotherapy as second-line treatment for advanced esophageal squamous cell carcinoma (ESCC) patients (pts). However, the PD-L1 expression by tumor proportion score (TPS) did not obviously correlate to the efficacy. In contrast, PD-L1 expression by combined positive score (CPS) was used as a companion diagnosis for pembrolizumab in ESCC. There are little data on CPS with nivolumab in ESCC. Methods: We retrospectively reviewed the medical records of the pts with ESCC who received nivolumab monotherapy in our hospital. The CPS before nivolumab was evaluated by 22C3 antibody. We evaluated the correlation of CPS and clinical efficacy of progression-free survival (PFS), overall response rate (ORR), disease control rate (DCR) by using Cox proportional regression model and Fisher’s exact test. Results: Eighty-seven pts were selected for this analysis with a median follow-up time of 7.9 (1.2-84.1) months. Thirty pts (34.5%) had CPS < 10, and 57 patients (65.5%) had CPS≥10. Between two groups, the characteristics were as follows; median age (range): 62 (35-85) and 66 (46-85) years, PS 0: 20.0/36.8%, prior taxane: 50.0/40.4%, prior radiotherapy: 86.7/77.2%, respectively. The median PFS (95%CI) were 1.8 (1.2-2.8)/2.6 (1.8-33.8) months (HR: 0.85 [0.52-1.38], p = 0.50). The ORR/DCR were 21.1/31.6% in CPS < 10 group, and 22.2/57.8% in CPS≥10 group, and there was no statistical significance, respectively (p = 1.0/0.10). In multivariate analysis, only higher age was the favorite factor for PFS. From the result with another cut-off level of CPS, the proportion of CPS≥1/CPS≥20 was 90.8/36.8%. The HR of multivariate analysis with CPS≥1/CPS≥20 was 1.24/0.73, respectively. Conclusions: There was a trend toward better PFS with a higher cut-off point of CPS. CPS had the potential to be a biomarker even for nivolumab for advanced ESCC pts.