3090 - Radiotherapy Combined with Chemoimmunotherapy vs. Chemoimmunotherapy Alone As First-Line Treatment for Advanced Esophageal Squamous Cell Carcinoma with Oligometastasis at Initial Diagnosis

X. Lv¹, S. Wang², W. Zhang³, Q. Pang⁴, Q. Lin⁵, Y. Wu⁶, Z. Hui⁷, Y. Liu⁸, Y. Cheng¹, Q. Liu⁹, and J. Wang⁶; ¹Fourth Hospital of Hebei Medical University, Shijiazhuang, China, ²the Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei, China, ³Tianjin Medical University Cancer Institute & Hospital,National Clinical Research Center for Cancer, Tianjin’s Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy,Tianjin, Tianjin, China, ⁴Department of Radiation oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention Therapy, Tianjin, Tianjin, China, ⁵North China Petroleum Bureau General Hospital, Hebei Medical University, Renqiu, Hebei, China, ⁶Department of Radiation Oncology, the Fourth Hospital of Hebei Medical University, Shijiazhuang, China, ⁷Department of VIP Medical Services, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, ⁸Department of Pathology, the Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei, China, ⁹Department of Radiotherapy, Fourth Hospital of Hebei Medical University, Shijiazhuang, China

Purpose/Objective(s): This study aims to assess the safety and efficacy of radiotherapy combined with chemoimmunotherapy (RCIT) versus chemoimmunotherapy (CIT) alone as the first-line treatment for oligometastatic esophageal squamous cell carcinoma (OESCC) at initial diagnosis. Materials/

Methods: A retrospective analysis of 140 patients diagnosed with OESCC and treated with either RCIT or CIT as their first-line treatment from June 2018 to December 2021 was conducted. There were 76 patients in the RCIT group and 64 in the CIT group. All patients were treated with anti-PD-1 monoclonal antibodies (mAbs), including pembrolizumab, nivolumab, camrelizumab, toripalimab, sintilimab, and tislelizumab. Propensity score matching (PSM) was utilized to simulate random allocation.
Results: Following 1:1 PSM, 61 well-paired patients were selected. The median follow-up was 16.6 months. Post-PSM analysis revealed significant differences in progression-free survival (PFS) [10.9 (95% CI: 9.4-12.4) vs. 7.3 (95% CI: 6.0-8.7) months, P=0.004] and overall survival (OS) [22.4 (95% CI: 17.5-27.4) vs. 13.4 (95% CI: 10.9-15.9) months, P=0.031] between the RCIT and CIT groups. Patients in The RCIT group have a lower probability of experiencing locoregional failure compared to the CIT group (36.1% vs 54.1%; ?²=4.006, P=0.045). In the subgroup analysis of PFS, patients with male gender (HR:0.600, P=0.018), age = 65 years old (HR:0.434, P=0.002), ECOG performance status of 0-1 (HR:0.589, P=0.008), BMI =18.5 (HR:0.603, P=0.016), clinical T stage of 2-3 (HR:0.544, P=0.006), clinical N stage of 1-2 (HR:0.554, P=0.007), extra-regional lymph node metastasis only (HR:0.556, P=0.017), 1-2 metastatic lesions (HR:0.441, P=0.003), single metastatic organ (HR:0.607, P=0.019), = 4 chemotherapy cycles (HR:0.517, P=0.007), and = 4 immunotherapy cycles (HR:0.554, P=0.023) or <4 immunotherapy cycles (HR:0.561, P=0.048) experienced significantly prolonged PFS in the RCIT group. In the subgroup analysis of OS, patients with male gender (HR:0.593, P=0.034), age = 65 years old (HR:0.556, P=0.042), <4 chemotherapy cycles (HR:0.489, P=0.037), and <4 immunotherapy cycles (HR:0.428, P=0.007) exhibited significantly prolonged OS in the RCIT group. no significant differences in the incidence of grade 3 or higher (G3+) treatment-related adverse events (TRAEs) were observed between the two groups. However, the incidence of G3+ pneumonitis (13.1% vs 1.6%, P=0.038) were higher in the RCIT group compared to the CIT group.
Conclusion: RCIT as first-line treatment for OESCC was safe and efficacious. RCIT improved PFS/OS compared to CIT without increasing the overall high-grade toxicity rate. However, the increased incidence of pneumonitis due to RT implementation cannot be disregarded.