MDPI AG Acta Medica Okayama 2072-6694 18 7 2026 Predictive Nomogram for Recurrence After Upfront Surgery for Resectable Pancreatic Ductal Adenocarcinoma: A Multicenter Study (OS-HBP-2) 1181 EN Ryuichi Yoshida Department of Gastroenterological Surgery, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences Kosei Takagi Department of Gastroenterological Surgery, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences Kazuya Yasui Department of Gastroenterological Surgery, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences Masayoshi Hioki Department of Surgery, Fukuyama City Hospital Takehiro Okabayashi Department of Surgery, Kochi Health Sciences Center Toru Kojima Department of Surgery, Okayama Saiseikai General Hospital Yoshikatsu Endo Department of Surgery, Himeji Red Cross Hospital Daisuke Nobuoka Department of Surgery, Fukuyama City Hospital Kenta Sui Department of Surgery, Kagawa Prefectural Hospital Masaru Inagaki Department of Surgery, National Hospital Organization Fukuyama Medical Center Susumu Shinoura Department of Surgery, Tsuyama Chuo Hospital Masashi Kimura Department of Surgery, Matsuyama Shimin Hospital Tatsuo Matsuda Department of Surgery, Tenwakai Matsuda Hospital Hideki Aoki Department of Surgery, National Hospital Organization Iwakuni Clinical Center Toshiyoshi Fujiwara Department of Gastroenterological Surgery, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences Background/Objectives: Postoperative recurrence is a critical issue in the treatment of resectable pancreatic ductal adenocarcinoma (rPDAC). Moreover, the prognosis after early recurrence is extremely poor. This study aimed to develop a recurrence prediction model and to define early recurrence after upfront surgery (UFS) for rPDAC. Methods: This multicenter retrospective study included patients who underwent UFS for anatomically rPDAC between January 2013 and December 2017. Multivariate analyses were conducted to identify the risk factors for recurrence-free survival and to construct a recurrence prediction model. Subsequently, a minimum p value approach was used to determine the optimal cutoff values for early and late recurrence. Results: The cohort included 603 patients (325 men and 278 women). During the median follow-up period of 25 months (interquartile range, 15–38 months), 381 patients (63.2%) experienced a recurrence. Multivariate analyses revealed carbohydrate antigen 19-9 ≥37 U/mL (hazard ratio [HR], 1.58; p < 0.001), tumor size ≥ 2.2 cm (HR, 1.59; p < 0.001), lymph node metastasis (HR, 1.86; p < 0.001), R1 resection (HR, 1.56; p = 0.002), and no adjuvant chemotherapy (HR, 1.54; p < 0.001) as independent predictors. The recurrence prediction model demonstrated an area under the curve of 0.72–0.75. The optimal threshold for early and late recurrences was a recurrence-free interval of five months. Carbohydrate antigen 19-9 ≥ 156 U/mL was a significant predictor of early recurrence (OR, 3.28; p < 0.001). Conclusions: This study identified the prognostic risk factors for recurrence and developed a recurrence prediction model for patients undergoing UFS for rPDAC. Moreover, a recurrence-free interval of five months was identified as the optimal threshold for distinguishing between early and late recurrences. No potential conflict of interest relevant to this article was reported.