Abstract No. 340 Incidence of Bland Portal-Mesenteric Venous Thrombosis After Y90 Radiation Segmentectomy

Bland porto-mesenteric vein thrombosis (PMVT) is a known complication of cirrhosis; however, its association with yttrium-90 (Y90) radiation segmentectomy (RS) has not been reported. We report the association of PMVT to Y90 RS in a retrospective cohort. In total 116 consecutive patients (64 men, median age 67.1 [IQR 62.5-72.3]) with HCC and no prior PMVT treated between 2017-2022 were included. Patients were Child-Pugh A5 (n=55), A6 (n=34), B7 (n=12), B8 (n=10), B9 (n=3), C10 (n=1), and C11 (n=1); 86 had solitary BCLC 0/A stage disease, 22 with multifocal BCLC A, and 8 with BCLC B. Incidence and distribution of PMVT following Y90 RS was tabulated, and severity was graded in accordance with CTCAE v5.0. Determinants of post-Y90 RS PMVT were analyzed using Kaplan-Meier and Cox proportional hazards methods. Patients were censored to repeat locoregional or curative therapy. PMVT occurred in 15/116 patients (13%) at a mean of 5.4±3.4 months post Y90 treatment; in 11/15 patients it occurred prior to any secondary locoregional therapy. Most cases (n=11) occurred within 6 months and in 7 cases within 3 months of Y90 RS. In 4/15 cases, it was associated with CTCAE 3+ adverse events requiring hospitalization due to pain (n=2) and hepatic decompensation (n=2). Patients with PMVT were predominantly Child-Pugh B7 or greater (n=10) and had thrombosis within the intrahepatic portal veins (n=9), main portal vein (n=9) and mesenteric vein (n=3). Intrahepatic portal vein thrombi occurred ipsilateral to the treatment site. In 5/15 cases, thrombosis was occlusive in the MPV or MV. Significant univariate predictors of PMVT were history of previous Y90 RS (OR 1.6, p = 0.03), higher CP score (HR 2.0, p = 0.01), higher ALBI grade (HR 2.3, p = 0.01), and percent of total treated liver (HR 1.6, p = 0.05). BCLC stage was not a significant univariate predictor of PMVT (p=0.8). On multi-variate analysis only CP score was a statistically significant predictor of PMVT (HR 1.8, p = 0.01). On Kaplan-Meier analysis, patients with Child-Pugh B7 or greater liver disease had lower probability of PMVT free survival (HR = 0.3, p= 0.04). Porto-mesenteric venous thrombosis occurs after Y90 RS in a substantial minority of cases, more frequently in patients with advanced liver disease, and may be associated with adverse clinical outcomes.