Preoperative pembrolizumab combined with chemoradiotherapy for esophageal squamous cell carcinoma: Trial design

The safety and feasibility of preoperative pembrolizumab combined with chemoradiotherapy (PPCT) for resectable esophageal squamous cell carcinoma have been confirmed by the prior Preoperative Anti-PD-1 Antibody combined with Chemoradiotherapy for Locally Advanced Squmous Cell Carcinoma of Esophageus (PALACE)-1 trial. Potential therapeutic benefit was also observed with a pathologic complete response rate of 55.6% after PPCT. We will conduct the multicenter single-arm PALACE-2 study to investigate the efficacy and to further confirm the safety of PPCT (ClinicalTrials.gov ID: NCT04435197).

A total of 143 patients with previously untreated, locally advanced, and surgically resectable esophageal squamous cell carcinoma (T2 through T4a, N0 through N+, M0) will be enrolled in PALACE-2. Main exclusion criteria are autoimmune disease, interstitial lung disease, ongoing immunosuppressive therapy, and having received chemotherapy, radiotherapy, target therapy, or immune therapy for this or any other malignancies. Positive programmed cell death ligand 1 expression is not mandatory for enrollment. Patients will receive PPCT, which includes concurrent pembrolizumab (200 mg on day 1 and day 22), carboplatin (area under the curve = 2, once a week for 5 weeks), nab-paclitaxel (50 mg/m², once a week for 5 weeks), and radiotherapy (23 fractions of 1.8 Gy, 5 fractions a week). Esophagectomy will be performed within 4 to 6 weeks after the completion of PPCT.

The primary end point is the rate of pathologic complete response. Secondary outcome measures are 3-year disease-free survival rate, 3-year overall survival rate, R0 resection rate, and adverse events during neoadjuvant and perioperative periods.

PPCT was preliminarily demonstrated to be safe, feasible, and to provide potential therapeutic benefits by the PALACE-1 trial. The subsequent multicenter PALACE-2 study will investigate the efficacy and further confirm the safety of PPCT for locally advanced, resectable esophageal squamous cell carcinoma.