413. LYMPH NODE MAJOR PATHOLOGIC RESPONSE IS A POTENTIAL PROGNOSTIC FACTOR AFTER NEOADJUVANT CHEMORADIOTHERAPY IN ESOPHAGEAL SQUAMOUS CELL CARCINOMA

Abstract Background Esophageal cancer ranks tenth in incidence and is the sixth most common cause of cancer-related deaths. Neoadjuvant chemoradiotherapy before and after surgery has been shown to improve ESCC patients' survival compared with surgery alone. However, the outcomes of nCRT are heterogeneous, and clinical or pathological methods that can predict nCRT responses have been extensively studied. There are currently no standard grading methods that assess the treatment response in lymph nodes after nCRT. We aimed to assess the clinicopathological relevance and determine the prognostic significance of lymph node major pathologic response (MPR) after nCRT in ESCC patients. Methods Patients who received nCRT for ESCC followed by surgery were retrospectively reviewed and classified into different lymph node stage (LNS) according to their pathological regression: LNS0 (no tumor cells in lymph node before nCRT); LNS1 (residual tumor cells in lymph node after nCRT≤50%; major pathologic response); LNS2 (residual tumor cells in lymph node after nCRT>50%; not major pathologic response). Results In total, 187patients, comprising 91,49 and 47 patients with LNS stage of 0(no tumor cells in lymph node before nCRT),1(major pathologic response), or 2(not major pathologic response), respectively, were included. The result showed that the higher LNS stage was strongly associated with decreased overall survival (P<0.001) and disease-free survival (P<0.001), and increased recurrence risks (P=0.002). The cox regression showed MPR was significantly an independent prognostic factor of OS and DFS. Among 96 patients with clinically positive LNs,54patients (56.3%) showed discordance between the PT and LN pathological regression grades. Conclusions Residual tumor cells in lymph node after nCRT≤50% could be defined as lymph node major complete response. The Lymph node MPR can be an independent prognostic indicator of ESCC patients who received nCRT plus curative surgery.