799. OPTIMUM NUMBERS OF DISSECTED LYMPH NODES FOR ACCURATE NODAL STAGING IN CT1-2N0 ESOPHAGEAL SQUAMOUS CELL CARCINOMA

Abstract Background Patients with esophageal squamous cell carcinoma (ESCC) with lymph node metastasis may be misclassified as pN0 due to an inadequate lymph node dissection. The purpose of this study was to confirm that patients with cT1-2N0 ESCC are indeed pN0 and to propose an adequate number of lymph nodes for correct nodal staging. Methods A total of 1,855 patients who underwent upfront surgery for cT1-2N0 ESCC at two tertiary academic hospital in Korea between 1995 and 2019 were included in the study. The probability of false-negative lymphadenectomy and NSS (nodal staging score) was calculated to assess the probability of pN0 status. Results The mean age was 63.36 ± 8.01 years, with 1,726 (93.05%) male patients. The mean number of dissected lymph nodes was 34.69 ± 13.98. The clinical T stages were as follows: cTis & cT1a 354 (19.08%), cT1b 1,053 (56.77%), and cT2 448 (24.15%). Pathologic nodal upstaging occurred in 443 (23.91%); pN1 352 (19.0%), pN2 78 (4.21%), and pN3 13 (0.7%). By calculating the probability of false-negative lymphadenectomy, removing fewer than 33 lymph nodes was associated with a 20% risk of missing a positive lymph node, whereas removing 53 lymph nodes was associated with a 10% risk of missing a positive lymph node. The NSS, which reflects the probability that a patient with ypN0 status is actually free of occult nodal disease after surgery, increased as the number of dissected lymph nodes increased. Conclusions Extensive lymph node dissection is mandatory for accurate staging and reducing the risk of missing positive lymph nodes in early-stage ESCC. The survival benefits of extensive lymph node dissection need to be evaluated in further analysis.