Clinical Significance of Lymph Node Dissection and Lymph Node Metastasis in Primary Appendiceal Tumor Patients After Curative Resection: a Retrospective Multicenter Cohort Study.

Purpose: Due to its rarity and biological heterogeneity, guidelines for primary appendiceal tumor (PAT) are based on scarce evidence, resulting in no strong recommendations. The present study explored prognosis-related factors, including the timing of lymph node dissection (LND), in PAT patients after curative resection (CR) to determine the optimal surgical therapies. Methods: We retrospectively collected and analyzed data from 404 patients with PATs who underwent CR at 43 tertiary hospitals from 2000 to 2017. This manuscript is based on revised manuscript during review process. Please, change the bold characters to normal characters in the manuscript. Results: After propensity score matching, there were no marked differences in the recurrence-free survival (RFS) or overall survival (OS) between the primary and secondary LND groups (P = 0.993 and 0.728). A multivariate analysis showed that lymph node metastasis (LNM) was an independent factor for the RFS (hazard ratio [HR] 2.59; 95% confidence interval [CI] 1.09–6.13; P = 0.031) and OS (HR 4.70; 95% CI 1.40–15.76; P = 0.012). There were significant associations between the LNM rates and tumor depth (P < 0.0001) and the histological type (P = 0.006). There was no LNM in patients with low-grade appendiceal mucinous neoplasm (LAMN) or well-differentiated mucinous adenocarcinoma (G1) or patients with any Tis or T1 PATs. Conclusions: LNM was an independent prognostic predictor in PATs after CR with LND. Tumor depth and histological type were not prognostic predictors but were LNM predictors. Secondary LND based on the pathological findings of resected specimens is considered an acceptable surgical management without a worse prognosis than primary LND, and it may be omitted in LAMN+G1 or in any Tis and T1 PATs. [ABSTRACT FROM AUTHOR]