Supplementary Material for: Risk Factors for Recurrence in Pancreatic Neuroendocrine Tumor and Size as a Surrogate in Determining the Treatment Strategy: A Korean Nationwide Study

<b><i>Introduction:</i></b> The prognostic factors of pancreatic neuroendocrine tumor (PNET) are unclear, and the treatment guidelines are insufficient. This study aimed to suggest a treatment algorithm for PNET based on risk factors for recurrence in a large cohort. <b><i>Methods:</i></b> Data of 918 patients who underwent curative intent surgery for PNET were collected from 14 tertiary centers. Risk factors for recurrence and survival analyses were performed. <b><i>Results:</i></b> The 5-year disease-free survival (DFS) rate was 86.5%. Risk factors for recurrence included margin status (R1, hazard ratio [HR] 2.438; R2, HR 3.721), 2010 WHO grade (G2, HR 3.864; G3, HR 7.352), and N category (N1, HR 2.273). A size of 2 cm was significant in the univariate analysis (HR 8.511) but not in the multivariate analysis (<i>p</i> = 0.407). Tumor size was not a risk factor for recurrence, but strongly reflected 2010 WHO grade and lymph node (LN) status. Tumors ≤2 cm had lower 2010 WHO grade, less LN metastasis (<i>p</i> &lt; 0.001), and significantly longer 5-year DFS (77.9 vs. 98.2%, <i>p</i> &lt; 0.001) than tumors &gt;2 cm. The clinicopathologic features of tumors &lt;1 and 1-2 cm were similar. However, the LN metastasis rate was 10.3% in 1-2-cm sized tumors and recurrence occurred in 3.0%. Tumors &lt;1 cm in size did not have any LN metastasis or recurrence. <b><i>Discussion/Conclusion:</i></b> Radical surgery is needed in suspected LN metastasis or G3 PNET or tumors &gt;2 cm. Surveillance for &lt;1-cm PNETs should be sufficient. Tumors sized 1-2 cm require limited surgery with LN resection, but should be converted to radical surgery in cases of doubtful margins or LN metastasis.