P9-7 Treatment outcome following nivolumab therapy administered after radiation therapy for esophageal cancer

Nivolumab is an immune checkpoint inhibitor that has been approved since February 2020 for the treatment of unresectable advanced/recurrent esophageal cancer that has worsened after initial chemotherapy. Although the treatment response rate is low at approximately 20%, it has been reported that the administration of nivolumab after irradiation enhances the antitumor effect in cases of esophageal and head and neck cancers. Therefore, we examined cases of nivolumab administration after irradiation of esophageal tumors in our department. To determine the therapeutic effect of nivolumab, we compared the treatment outcomes, including adverse events, between the patients without (NR group) and those with a history irradiation (R group) among 28 patients who received nivolumab for esophageal cancer between April 2020 and August 2021. The NR group included 17 cases; and the R group, 11 cases. No significant differences in patient background and incidence of adverse events were found between the two groups. The best overall effects were complete response/partial response/stable disease/progressive disease as follows: 1/2/4/10 (response rate, 17.7%: disease control rate, 41.2%) in the NR group and 2/3/3/3 (response rate, 45.5%: disease control rate, 72.7%) in the R group, with no significant differences between the groups (p = 0.35). However, a high response rate tended to be observed in the R group. The progression-free survival time at a median observation period of 261.5 days was 100.2 ± 96.6 days in the NR group and 181.9 ± 135.3 days in the R group (p = 0.07). Nivolumab administration after irradiation of esophageal cancer exhibited an improved therapeutic effect in the patients in this study.