2990 - Pattern of Primary Tumor Residual and Lymph Node Spread in Esophageal Squamous Cell Carcinoma Treated with Neoadjuvant Chemoradiotherapy with or without Pembrolizumab

X. Han^1,2, W. Qi^1,2, S. Li^1,2, H. Li^1,2, F. Xu^1,2, J. Chen^1,2, and S. Zhao^1,2; ¹Department of Radiation Oncology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China, ²Shanghai Key Laboratory of Proton-therapy, Shanghai, China

Purpose/Objective(s): Neoadjuvant concurrent chemoradiotherapy (NCRT) is recommended as the standard-of-care for locally advanced esophageal squamous cell carcinoma (ESCC). Adding immunotherapy to NCRT (NICRT) has gained attention in clinical practice. We evaluated the differences in clinicopathologic outcomes and the patterns of lymphatic spread in patients receiving NCRT and NICRT before esophagectomy for locally advanced ESCC. Materials/

Methods: A total of 209 patients with locally advanced ESCC who completed transthoracic esophagectomy after neoadjuvant treatment were enrolled from two prospective cohorts. Clinicopathologic parameters, including pathologic complete response (pCR) and tumor regression grade (TRG) score, were recorded. The rates of lymph node metastasis in each station classified by both 8^th edition of American Joint Committee on Cancer (AJCC) esophageal cancer staging system and 11^th edition of Japanese Classification of Esophageal Cancer (JES) standard were evaluated.
Results: Compared with the NCRT group, the NICRT group had a numerically advantage in pathological response and primary tumor regression. The rate of pCR and complete primary tumor regression was 37.0% vs. 44.5% (P=0.284) and 43.2% vs. 49.2% (P=0.396), respectively. The NICRT strategy significantly reduced the risk of nerve invasion by tumor (3.9% vs. 11.1%, P=0.042). Compared with NCRT, NICRT can significantly reduce the rate of lymph node metastasis in station 2R (right upper paratracheal lymph nodes, 0.8% vs. 4.8%, P=0.038) classified by AJCC system, and station 106recR (right recurrent nerve lymph nodes, 0.8% vs. 4.8%, P=0.041) and station 20 (lymph nodes in the esophageal hiatus of the diaphragm, 0 vs. 14.3%, P=0.030) classified by JES standard. Subgroup analysis according to the tumor location showed that NICRT group had lower metastasis rate in lower thoracic paraesophageal lymph nodes (0% vs. 9.7%, P=0.033) in middle thoracic cases.
Conclusion: NICRT followed by surgery may lead to a promising pathological response. For patients with lymph nodes metastasis in certain regions, NICRT should be considered as a better preoperative treatment option.