Camrelizumab (Camre) plus taxane-based chemotherapy (CT): Clinical outcomes and dynamic monitoring of CEA as a predictive biomarker of response in patients with recurrent or advanced esophageal squamous cell carcinoma (ESCC).

e16524 Background: Keynote-181 study reported anti-PD-1 antibody pembrolizumab as monotherapy had shown superior efficacy compared to CT for previously treated patients (pts) with advanced ESCC. The combination of anti-PD-1 antibody and CT may be a feasible approach to provide antitumor activity superior to either agent alone. However, the available data about the combination strategy is limited. Methods: We retrospectively reviewed the records of pts treated at our center to identify pts seen between 7/2019 and 12/2019 with recurrent or metastatic ESCC who received treatment with Camre (anti-PD-1 antibody) plus taxane-based CT. The primary endpoints were objective response rate (ORR) and disease control rate (DCR) per RECIST 1.1. Secondary endpoint included toxicity. The carcinoembryonic-antigen (CEA) dynamics and clinical associations were also evaluated in the selected pts. Results: A total of 14 pts were identified. The median age was 66 years (44-80). Most pts were male (12/14, 85.7%) with metastatic disease (10/14, 71.4%). The CT regimens contained nab-paclitaxel in 4 pts, nab-paclitaxel plus nedaplatin in 2, liposomal paclitaxel in 2, liposomal paclitaxel plus nedaplatin in 6. Camre in combination with CT were repeated every 3 to 4 weeks for up to 4 cycles. Two pts also received maintenance therapy of Camre for 4 and 6 cycles. Five pts (35.7%) exhibited a best overall response of PR, 6 (42.9%) SD, and 3 (21.4%) PD. The ORR and DCR were 35.7% (5/14) and 78.6% (11/14), respectively. All the SD determination as the best response met the minimum interval of 8 weeks from baseline. Toxicity profile was mild with mainly grade 1, expected toxicities. The most common grade 3/4 adverse events were leucopenia (2/14, 14.3%) and neutropenia (2/14, 14.3%). CEA baseline levels were normal in 6 cases, elevated in 8. It was observed that CEA levels closely paralleled overall measurable tumor burdens in all the CEA-elevated pts. A patient with equivocal radiographic pseudoprogression even had CEA dynamics that correlated with eventual clinical outcome. Conclusions: We identified a group of pts of recurrent or metastatic ESCC treated with Camre plus taxane-based CT and achieving a favorable DCR to therapy with a tolerable toxicity profile. This combination regimen warrants further exploration in a prospective clinical trial. CEA dynamics may be a useful tool to monitor disease evolution in this setting.