Nivolumab for esophageal squamous cell carcinoma and the predictive role of PD-L1 or CD8 expression in its therapeutic effect

Introduction Nivolumab, a programmed death 1 (PD-1) inhibitor, has recently demonstrated efficacy as second-line therapy for esophageal squamous cell carcinoma (ESCC) patients in a phase III trial. We report real-world clinical outcomes of nivolumab therapy for ESCC patients. Methods ESCC patients refractory/intolerant to at least one line of chemotherapy and who received nivolumab as a subsequent line of therapy were included. The efficacy and safety of nivolumab and the predictive role of PD-L1 and CD8 expression were analyzed. Results Fifty-eight patients were analyzed for safety and survival outcomes, while 57 were analyzed for objective response rates (ORR) excluding one with no measurable lesions. Eleven patients achieved a partial response, leading to an ORR of 19.3%. The median response duration was 6.5 months (range 4.1-22.4). The median progression-free survival (PFS) and overall survival were 2.1 (95% confidence interval [CI] 1.8-2.3) and 7.4 (95% CI 4.8-10.0) months, respectively. Among patients with adequate samples, 56.9% (29/51), 27.5% (14/51), and 17.6% (9/51) expressed a combined positive score (CPS) >= 1, >= 10, and >= 20, respectively, while 24.4% (11/45) and 57.5% (23/40) were positive for intratumoral and peritumoral CD8 + T cell infiltration, respectively. A significantly longer PFS was observed in patients with a CPS >= 20 (7.5 [95% CI 1.8-13.1] vs. 1.9 [1.4-2.3] months, P = 0.05), and a trend towards better survival was seen in those with CPS >= 10 or intratumoral CD8 + T cell infiltration. Conclusions Nivolumab is a valuable option at subsequent treatment lines for patients with advanced ESCC.