S1103
Clinical – Upper GI
ESTRO 2026
Hospital, Suwon, Korea, Republic of. 6 Division of Gastrointestinal Surgery, Department of Surgery, Uijeongbu St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of. 7 Department of Hospital Pathology, Uijeongbu St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of Purpose/Objective: Selecting intramucosal gastric cancer for endoscopic resection demands accurate prediction of LN metastasis. Current guidelines show critical limitations; in our multi-institutional cohort (N=2,098), 93.6% of patients recommended for surgery were LN negative (6.4% specificity), while six (0.4%) patients deemed curative (eCura A) had LN metastasis. Tumor budding is a known prognostic factor, but its utility in intramucosal gastric cancer is debated, especially in diffuse-types involving signet-ring cells. We investigated if a modified tumor budding, which excludes signet-ring cells, could improve prognostic accuracy over conventional tumor budding. Material/Methods: From the total cohort, we constructed a 1:5 propensity score-matched cohort (N=306; 51 with lymph node metastasis, 255 without). We defined modified tumor budding as tumor buds excluding signet-ring cell morphology. The predictive performance of conventional tumor budding and modified tumor budding (using binary, consensus conference, and total-count methods) for LN metastasis was compared using multivariate logistic regression and Area Under the Curve analysis. Results: Tumor budding composed only of signet-ring cells was not associated with LN metastasis (p>0.3). Critically, of the six LN positive cases missed by the eCura A guideline, conventional tumor budding detected all six (100% sensitivity), while modified tumor budding detected five (83.3%). Despite this, modified tumor budding demonstrated superior overall predictive performance. The total-count method for modified tumor budding showed the highest accuracy (Area Under the Curve: 0.804 vs 0.767 for the conventional total-count) and was a powerful independent predictor (Odds Ratio 63.93, p<0.001). This method also showed 'almost perfect' interobserver agreement (Kappa=0.813). Conclusion: Modified tumor budding, by excluding prognostically irrelevant signet-ring cell buds, is a superior and highly reproducible predictor of LN metastasis in intramucosal gastric cancer compared to conventional tumor budding. The modified total-count method is a robust tool that can complement current guidelines to improve patient selection for curable endoscopic resection.
11-40) after ENI. One- and two-year OS for IFRT were 55% and 15%, versus 49% and 14% for ENI, respectively. Pooled grade 3-4 adverse events included nausea and vomiting (IFRT: 6%, 95% CI: 3-10; ENI: 5%, 95% CI: 0-18) and diarrhea (IFRT: 3%, 95% CI: 1-5; ENI: 4%, 95% CI: 1-16).In the only comparative study reviewed, 1-year OS was significantly higher in the IFRT group versus the ENI group, 51% versus 34% (p=0.04), respectively. This OS benefit was maintained at 3 and 5 years. Although both groups reported grade 3-5 toxicities, this did not significantly differ between groups. Conclusion: The current available evidence suggests that both IFRT and ENI have similar rates of LRF. OS and objective tumor response are potentially higher in IFRT, while rates of severe nausea and vomiting, as well as diarrhea, do not appear to differ. Further investigation is warranted to establish the optimal volumes for nodal irradiation within chemoradiation protocols for locally advanced pancreatic cancer. References: 1. Umezawa R, Ito Y, Wakita A, et al. How Much Was the Elective Lymph Node Region Covered in Involved- Field Radiation Therapy for Locally Advanced Pancreatic Cancer? Evaluation of Overlap Between Gross Target Volume and Celiac Artery-Superior Mesenteric Artery Lymph Node Regions. Adv Radiat Oncol. 2019;5(3):377-387. Published 2019 Sep 13. doi:10.1016/j.adro.2019.08.0142. Shi C, De B, Tran Cao HS, et al. Escalated-dose radiotherapy for unresected locally advanced pancreatic cancer: Patterns of care and survival in the United States. Cancer Med. 2024;13(12):e7434. doi:10.1002/cam4.7434 Keywords: Pancreatic Cancer, Nodal Irradiation Tumor budding predicts endoscopically curable intramucosal gastric cancer: A multi-institutional study of LN metastasis Sea-Won Lee 1 , Young Sub Lee 2 , Sung Hak Lee 3 , Jae Myung Park 4 , Yujin Lee 5 , Eun Young Kim 6 , Kwangil Yim 7 1 Department of Radiation Oncology, Eunpyeong St. Mary's Hospital, College of Medicine, the Catholic University of Korea, Seoul, Korea, Republic of. 2 Department of Hospital Pathology, Eunpyeong St. Mary's Hospital, College of Medicine, the Catholic University of Korea, Seoul, Korea, Republic of. 3 Department of Hospital Pathology, Seoul St. Mary's Hospital, College of Medicine, the Catholic University of Korea, Seoul, Korea, Republic of. 4 Division of Gastroenterology, Department of Internal Medicine, Seoul St. Mary's Hospital, College of Medicine, the Catholic University of Korea, Seoul, Korea, Republic of. 5 Department of Hospital Pathology, St. Vincent's Digital Poster 3641
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