LAUSR

BACKGROUND We advocated carbohydrate antigen (CA) 19-9 ≥ 150 U/mL and tumor size ≥ 30 mm as "high-risk markers" for predicting unresectability among patients with radiologically resectable (R) or borderline resectable (BR) pancreatic ductal adenocarcinoma (PDAC). The main aim is to establish a risk scoring system for occult abdominal metastasis (OAM) in R/BR PDAC. METHODS Predictors of OAM were investigated retrospectively in an experiment cohort from 2006 to 2018. The proposed risk scoring system was validated in another cohort from 2019 to 2020. RESULTS Eligible 513 patients were divided into the experimental (405 patients; OAM, 22%) and validation cohorts (108 patients). Multivariate analysis identified tumor location of body/tail (odds ratio [OR] 4.45, p < 0.0001) and "high-risk markers" (OR 2.07, p = 0.011) as independent predictors of OAM. A scoring system consisting of body/tail (yes: 1, no: 0) and "high-risk markers" (yes: 1, no: 0) was constructed. In the validation cohort, when staging laparoscopy (SL) was performed for patients with scores 1/2, the eligibility for SL, sensitivity, and negative predictive value of OAM were 55%, 91%, and 96%, respectively. CONCLUSIONS Tumor location of body/tail and "high-risk markers" were independent predictors of OAM, composing our simple and reproducible risk scoring system.