Evaluation of pembrolizumab plus cisplatin and fluorouracil in radical treatment for patients with T4b esophageal squamous cell carcinoma.

Background: Pembrolizumab plus cisplatin and 5-fluorouracil administered as first-line therapy for advanced esophageal cancer patients has shown a better objective response and survival than conventional chemotherapy with less severe hematological adverse events. The safety and efficacy of this regimen were evaluated in patients with T4b esophageal squamous cell carcinoma (ESCC).

Methods: Eight consecutive patients with T4b ESCC received this regimen according to KEYNOTE-590 as induction, and they were evaluated after 1-3 courses. The programmed death-ligand 1 (PD-L1) combined positive score (CPS) was also evaluated before chemotherapy. Efficacy for the primary lesion was evaluated by our original formula for the tumor reduction rate.

Results: The numbers of patients with partial response (PR), stable disease, and progressive disease (PD) were 5, 1, and 2, respectively. The tumor reduction rate ranged from 69 to 87% in PR patients, and all PR patients had relief from T4b. Two patients underwent conversion surgery with R0 resection. PD-L1 CPS was over 90 in 2 PR patients, but under 10 in 2 other PR patients. PD-L1 CPS was under 10 in PD patients. One patient had hyperprogression, resulting in an esophago-pulmonary fistula. Greater than grade 3 adverse events were bleeding gastric ulcer in one patient (12.5%), neutropenia without G-CSF in 3 patients (37.5%), and hypopotassemia in 1 patient (12.5%). No patient had febrile neutropenia.

Conclusions: Marked tumor reduction was confirmed in 62.5% of patients with pembrolizumab plus cisplatin and 5-fluorouracil with less adverse events. This regimen could be administered as induction chemotherapy for patients with T4b ESCC.