NY-ESO-1 and PD-L1 as biomarkers associated with nivolumab response and outcome in unresectable or recurrent esophageal squamous cell carcinoma: a multicenter biomarker study

BACKGROUND: Programmed cell death protein-1 (PD-1) blockade improves survival in esophageal squamous cell carcinoma (ESCC), although only a subset of patients respond. We aimed to identify tumor-related biomarkers associated with response and outcome in patients with unresectable or recurrent ESCC. METHODS: This multicenter retrospective study included 250 patients with unresectable or recurrent ESCC who received nivolumab as second- or later-line therapy. Pretreatment tumor specimens were evaluated by immunohistochemistry for p53, NY-ESO-1, MLH1, and programmed death-ligand 1 (PD-L1). PD-L1 expression was assessed using both tumor proportion score (TPS) and combined positive score (CPS) by using automated digital image analysis. Associations with objective response, progression-free survival (PFS), and overall survival (OS) were analyzed. RESULTS: NY-ESO-1 expression was significantly associated with response to nivolumab (28.6% vs. 11.1%, P = 0.005) and remained independently associated with response in multivariate analysis (OR 3.32, 95% CI 1.49-7.28, P = 0.0027). PD-L1 expression was also associated with response according to both CPS and TPS. Patients with CPS ≥ 10% showed higher response rates than those with CPS < 10% (24.1% vs. 10.2%, P = 0.003), as well as longer median PFS (2.6 vs. 2.0 months, P = 0.0173) and OS (12.3 vs. 10.4 months, P = 0.0479). In contrast, p53 expression showed no significant association with response or survival, and MLH1 loss was rare. CONCLUSIONS: NY-ESO-1 expression was associated with response to nivolumab, while PD-L1 expression, particularly CPS, may provide clinically relevant prognostic information. Integrated assessment of tumor-related biomarkers and the host immune microenvironment may further improve patient stratification in ESCC.