Chemoimmunotherapy plus radiotherapy in advanced esophageal squamous-cell carcinoma.

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437 Background: Chemotherapy plus Immune checkpoint inhibitors (ICIs) have improved survival outcomes of patients with advanced or metastatic esophageal squamous-cell carcinoma in both first- and second-line settings. However, the benefit of additional radiotherapy for the residual esophageal lesion after chemo-immunotherapy remains unclear. Methods: We conducted a one-arm, three-center, open label study involving patients who were treatment naïve, radiological and histological confirmed advanced or metastatic squamous-cell esophageal carcinoma. Enrolled patients were expected the survival time was three months or longer; and ECOG performance status score was 0 or 1. In induction phase, patients received four cycles of TP regimen chemotherapy (docetaxel, 75/mg 2 , iv on day 1 and cisplatin, 75mg/m 2 , iv on day 1) combined with PD-1 inhibitor (sintilimab, 200mg intravenous infusion on day 1) every 21 days. Patients who finished four cycles of chemo-immunotherapy with stable disease (SD) or partial response (PR) were initiated 50Gy/25f irradiation for residual tumors. 3-4weeks after radiotherapy, maintenance sintilimab therapy was administered every 21 days for another 31 cycles or until disease progression or intolerable toxicity. Results: Total of 39 patients were enrolled in this study, 30 of them could be evaluated in efficiency and toxicities. All of them were male and were squamous-cell carcinoma in histology. 12/30 (40.0%) patients were in stage III, and 18/30 (60.0%) were in stage IV. 29/30 (96.7%) patients completed four cycles chemo-immunotherapy, the complete response (CR) rate was 6.7% (2/30), the partial response (PR) rate was 53.3% (16/30) and disease control rate (DCR) was 86.7% (26/30). The median depth of response (DpR) was 34.5% for chemoimmunotherapy and was 64.0% after radiotherapy. The progression-free survival (PFS) was 16.4 months and the overall survival (OS) was not reached. The most common grade 3 or worse adverse event was neutropenia and occurred in 3 (10.0%) patients. Conclusions: Four cycles sintilimab plus cisplatin and docetaxel followed by radiotherapy for residual tumors and maintained sintilimab had high response rate, prolonged PFS and tolerable toxicities as first line treatment in patients with advanced or metastatic esophageal squamous-cell carcinoma. Longer OS is promising and more patients enrolled in this study is needed in future. Clinical trial information: NCT06138028 . Clinicopathological features and patient factors. Factors No. of patients (n=30) (%) Gender Male 30 (100.0) Female 0 (0) Age (year) < 65 27 (43.3) ≥ 65 17 (56.7) PD-L1 (CPS) < 5 9 (30.0) ≥ 5 21 (70.0) Clinical Stage III 12 (40.0) IV 18 (60.0) Metastatic Pattern Regional lymph node 12 (40.0) Cervical & Supraclavicular 4 (13.3) Abdomen 5 (16.7) Lung 6 (20.0)