AbstractThe objective of this study was to evaluate the role of regional lymph node (LN) metastasis detected on preoperative CT and/or ¹⁸F-fluoro-2-deoxyglucose-positron emission tomography (FDG-PET) scans in the prediction of early tumor recurrence after curative surgical resection of pancreatic ductal adenocarcinoma (PDAC). This retrospective study included 137 patients who underwent upfront surgery with R0 resection of PDAC between 2013 and 2016. Regional LN metastasis was identified using two criteria: positive findings for regional LN metastasis on either preoperative CT or FDG-PET scans (LN_OR), or on both preoperative CT and FDG-PET scans (LN_AND). A total of 55 patients had early tumor recurrence within 12 months after curative resection. Univariable and multivariable Cox proportional hazard regression analysis showed that preoperative carbohydrate antigen 19–9 (CA19-9) levels, preoperative locally advanced status, and regional LN metastasis (both LN_OR and LN_AND criteria) were significant risk factors for early recurrence. Positive LN_OR and LN_AND showed significantly poorer recurrence-free survival compared to negative regional LN metastasis groups (p = 0.048 and p = 0.020, respectively). Compared with the LN_AND criteria, the LN_OR criteria provided higher sensitivity (22.4% vs. 15.5%, p = 0.046) and a higher negative predictive value (61.9% vs. 59.8%, p = 0.046). The LN_OR definition provided more sensitive and accurate performance in diagnosing preoperative regional LN metastasis.