Short-course neoadjuvant radiotherapy combined with chemotherapy and toripalimab for locally advanced esophageal squamous cell carcinoma (SCALE-1): a single-arm phase Ib clinical trial

Background The optimal dosages, timing, and treatment sequencing for standard-of-care neoadjuvant chemoradiotherapy necessitate re-evaluation when used in conjunction with immune checkpoint inhibitors for patients with resectable, locally advanced esophageal squamous cell carcinoma (RLaESCC). The SCALE-1 phase Ib study aimed to evaluate the safety and efficacy of short-course neoadjuvant radiotherapy combined with chemotherapy and toripalimab in this patient population.Methods RLaESCC patients with clinical stages cT3-4aN0M0/cT1-4aN+M0 received neoadjuvant paclitaxel (135 mg/m2), carboplatin (area under the curve=5), and toripalimab (240 mg) every 3 weeks for two cycles. Short-course neoadjuvant radiotherapy (30 Gy in 12 fractions; 5 days per week) was administered between neoadjuvant immune-chemotherapy (nICT) doses. Esophagectomies were scheduled 4–6 weeks after completing neoadjuvant treatment. The primary endpoint was safety, with secondary endpoints including pathological complete response (pCR) rate, postoperative complications, progression-free survival (PFS), and overall survival (OS). Exploratory biomarker analysis used gene expression profiles via the nCounter platform.Results Of the 23 patients enrolled, all completed neoadjuvant radiotherapy, while 21 cases finished full nICT doses and cycles. Common grade 3/4 adverse events included neutropenia (57%), leukopenia (39%), and skin rash (30%). No grade 3 or higher esophagitis or pneumonitis occured. Twenty patients underwent surgery, and 11 achieved pCR (55%). Two patients (10%) experienced grade IIIb surgical complications. At the database lock, a 2-year PFS rate of 63.8% (95% CI 43.4% to 84.2%) and 2-year OS rate was 78% (95% CI 64.9% to 91.1%) were achieved. Tumor immune microenvironment analysis indicated that tumors with pCR exhibited significantly higher pretreatment T-cell-inflamed score and post-treatment reshaping of antitumor immunity.Conclusions Combining short-course neoadjuvant radiotherapy with chemotherapy and toripalimab demonstrated favorable safety and promising efficacy in RLaESCC patients.Trial registration number ChiCTR2100045104.