Pembrolizumab versus chemotherapy as second-line therapy for advanced esophageal cancer: Phase III KEYNOTE-181 study.

2 Background: Patients with advanced esophageal cancer after first-line chemotherapy (chemo) have a poor prognosis and limited treatment options. We present results of the phase 3 KEYNOTE-181 study of pembrolizumab vs investigator’s choice chemo as second-line therapy for patients (pts) with advanced/metastatic squamous cell carcinoma (SCC) and adenocarcinoma of the esophagus or Siewert type I adenocarcinoma of the EGJ (NCT02564263). Methods: Eligible pts were randomized 1:1 to pembrolizumab 200 mg Q3W for up to 2 years or investigator’s choice chemo of paclitaxel, docetaxel, or irinotecan. Randomization was stratified by histology (SCC vs adenocarcinoma) and region (Asia vs rest of world). Primary end points were OS in the SCC, PD-L1 combined positive score (CPS) ≥10, and ITT populations. Results: 628 pts were randomized including 401 with SCC, and 222 with CPS ≥10. As of October 15, 2018, the median follow-up was 7.1 mo (pembrolizumab) vs 6.9 mo (chemo). Pembrolizumab was superior to chemo for OS in CPS ≥10 (N=222; median 9.3 vs 6.7 mo; HR 0.69; 95% CI 0.52-0.93; P=0.0074). The 12-mo OS rate in pts with CPS ≥10 was 43% vs 20%. There was clinically meaningful improvement in OS with pembrolizumab vs chemo in pts with SCC, but this was not statistically significant per prespecified boundaries (N=401; 8.2 mo vs 7.1 mo; HR 0.78; 95% CI 0.63-0.96; P=0.0095). In the ITT population, while directionally favorable, the difference in OS was not statistically significant (N=628; 7.1 mo vs 7.1 mo; HR 0.89; 95% CI 0.75-1.05; P=0.0560). Fewer pts had any-grade (64% vs 86%) or grade 3-5 (18% vs 41%) drug-related AEs with pembrolizumab vs chemo. Conclusion: Pembrolizumab significantly improved OS compared with chemo as second-line therapy for advanced esophageal cancer with PD-L1 CPS ≥10, with a more favorable safety profile. These data support pembrolizumab as a new second-line standard of care for esophageal cancer with PD-L1 CPS ≥10. The phase 3 KEYNOTE-590 study of pembrolizumab plus chemo as first-line therapy for advanced esophageal cancer is ongoing (NCT03189719). Clinical trial information: NCT02564263.