Intestinal Low-Dose Radiotherapy Plus Immunochemotherapy for Conversion of Borderline Resectable/Unresectable Esophageal Squamous Cell Carcinoma

Esophageal cancer (EC) ranks among the leading malignant gastrointestinal tumors globally in terms of both incidence and mortality. Cases of EC in China account for over 50% of the global total, with squamous cell carcinoma being the primary pathological type. Locally advanced EC (LAEC), particularly cases where radical surgical resection is not feasible, exhibits high recurrence rates and low 5-year survival rates. However, studies have shown that patients with LAEC who undergo comprehensive treatment followed by surgery experience significantly prolonged survival and improved quality of life compared to those who do not receive surgical intervention. Current conversion treatment regimens under investigation include: chemotherapy alone, chemoradiotherapy, immunotherapy combined with chemotherapy, and immunotherapy combined with chemoradiotherapy-each of these approaches has distinct advantages and limitations. Immunochemotherapy has emerged as a current research focus: it not only demonstrates significantly superior efficacy compared to chemotherapy alone but also exhibits lower cumulative toxicity than radiotherapy-combined conversion regimens, resulting in a more favorable overall benefit-risk ratio. As such, it represents the most promising conversion treatment strategy. Retrospective and prospective clinical studies have shown that low-dose radiotherapy targeting the small intestine can enhance the anti-tumor response of immune checkpoint inhibitors (ICIs) in patients with advanced solid tumor, prolong their overall survival, and increase the incidence of the abscopal effect. Further mechanistic investigations have revealed that intestinal low-dose radiotherapy (ILDR) may augment the immune cancerous lethality by modulating the gut microbiota and their metabolic profiles. Based on the findings from these preliminary studies, the current research plans to conduct a prospective phase II single-arm clinical trial to investigate the efficacy and safety of ILDR combined with immunochemotherapy as conversion therapy in patients with borderline resectable or unresectable esophageal squamous cell carcinoma (BR/UR ESCC). This research plans to enroll at least 39 evaluable cases or a total of 39 cases in two seperated stages, focusing on patients with thoracic BR/UR ESCC. Patients will receive a single fraction of ILDR with a mean dose of 1 Gy, concurrently with 3 cycles of albumin-bound paclitaxel (260 mg/m² on day 1), cisplatin (75 mg/m² on day 1), and tislelizumab (200 mg on day 1). The efficacy and safety of the treatment will be evaluated throughout the study.