575. PATHOLOGIC RESPONSE AND RESIDUAL LYMPH NODE PATTERNS IN ESOPHAGEAL SQUAMOUS CELL CARCINOMA PATIENTS UNDERGOING NEOADJUVANT IMMUNOCHEMOTHERAPY COMPARED TO NEOADJUVANT CHEMORADIOTHERAPY

Abstract Background Concurrent chemoradiotherapy is the cornerstone treatment for locally advanced esophageal cancer. Immunochemotherapy, established as the standard treatment for advanced esophageal cancer, concurrently exhibits excellent short-term efficacy in the neoadjuvant stage. Combining concurrent chemoradiotherapy with immunochemotherapy may enhance control over primary tumor and metastatic lymph nodes, potentially improving patients’ outcomes and survival. Therefore, comparing the pros and cons of these two treatment modalities in controlling primary lesions and lymph node metastasis is crucial for guiding clinical treatment. Methods Our study enrolled a total of 137 patients with esophageal squamous cell carcinoma (ESCC) who underwent neoadjuvant immunochemotherapy (NICT) and 151 ESCC patients who underwent neoadjuvant chemoradiotherapy (NCRT) between January 2019 and March 2022. We documented baseline patient characteristics, including clinical TNM stage, tumor location, and clinical metastatic lymph nodes, as well as pathologic outcomes such as pathological stage, pathologic complete response (pCR), tumor regression grade (TRG), and pathological metastatic lymph nodes. To balance baseline patient characteristics, we employed inverse probability of treatment weighting (IPTW) to adjust for confounding in different neoadjuvant treatment groups. Results After balancing baseline characteristics, there was no statistically significant difference in pathologic outcomes, including pCR rate, major pathologic response rate, TRG, yp-TNM stage, and R0 resection rate between NCRT and NICT. However, patients with clinical N2-3 stage (OR 2.66; 95% CI 1.05 to 6.79) or lower thoracic esophageal tumors (OR 2.31; 95% CI 1.05 to 5.04) had a higher chance of achieving pCR after NICT compared to NCRT. For patients undergoing NICT, the ypN0 rates for clinically N0 patients were 100.0% (5/5), while only 65.0% (13/20) of clinical N0 patients achieved ypN0 in the NCRT group. Even after adjusting for differences in clinical stage, tumor location, and baseline lymph node metastasis rates in various locations, the NICT group still demonstrated a lower rate of abdominal lymph node metastasis during surgery (p=0.030). Conclusion In comparison to concurrent chemoradiotherapy, immunochemotherapy exhibits comparable overall disease control for primary lesions and lymph node metastasis. Notably, patients with clinical N2-3 and lower thoracic esophageal cancer may derive greater benefits from NICT. The potential of immunochemotherapy in enhancing the effectiveness of chemoradiotherapy is evident in its ability to improve the control of occult metastatic lymph nodes and reduce abdominal lymph node metastasis.