Temporal Differentiation of Nonperipheral Washout Refines Prognostic Stratification in HCC

BACKGROUND AND AIMS: Nonperipheral washout is a major imaging feature of hepatocellular carcinoma (HCC) with prognostic value, but whether its temporal differentiation can refine prognostic stratification remains understudied. This study aimed to investigate the prognostic implications of nonperipheral washout timing in HCC. METHODS: This multicentre, retrospective cohort study included patients who underwent curative resection for single BCLC stage 0/A HCC and preoperative extracellular contrast agent-enhanced MRI at seven tertiary centres (March 2011 to April 2023). Three masked radiologists independently evaluated nonperipheral washout patterns, which were classified as early (present in the portal venous phase), late (present only in the delayed phase), or absent. Early recurrence-free survival (eRFS; ≤ 2 years) and 5-year RFS were assessed using Kaplan-Meier and Cox regression analyses. RESULTS: A total of 611 patients (median age, 55 years; 520 men) were included. Early, late, and no washout were observed in 367 (60.1%), 95 (15.5%), and 149 (24.4%) patients, respectively. Inter- and intra-reader agreements were substantial to excellent (κ range, 0.67-0.94). Early washout was associated with microvascular invasion (p = 0.01) and Edmondson-Steiner G3/4 (p = 0.002). The eRFS rates were 67.3%, 82.1%, and 85.2% for the early, late, and no-washout groups (p < 0.001); the 5-year RFS rates were 53.4%, 62.1%, and 71.8% (p = 0.002). In multivariable Cox analysis adjusting for factors, early washout independently predicted eRFS (HR, 1.86; p < 0.001) and 5-year RFS (HR, 1.46; p = 0.006). CONCLUSIONS: In patients undergoing curative resection for single BCLC 0/A HCC, temporal differentiation of nonperipheral washout refines prognostic stratification, with early washout identifying patients at higher risk of recurrence.