Change in total lesion glycolysis and clinical outcome after (90)Y radioembolization in intrahepatic cholangiocarcinoma

Our aim was to assess the prognostic value of post-treatment decrease in total lesion glycolysis (ΔTLG) assessed by 2-[(18)F]-fluorodeoxyglucose ([(18)F] FDG) PET-CT performed 6weeks after (90)Y radioembolization ((90)Y RE) in patients affected by intrahepatic cholangiocarcinoma (ICC).A total of 18 patients were accepted into our department for (90)Y RE. Before the procedure, all patients underwent [(18)F] FDG PET-CT, and total lesion glycolysis was calculated. Six weeks after (90)Y administration, PET scan was performed, and ΔTLG was determined. Patients underwent follow up by imaging and laboratory at quarterly intervals until death or for at least 24 months from (90)Y RE. Furthermore, subjects were divided in 2 groups (group 1: 6 weeks ΔTLG>50\%, group 2: ΔTLG<50\%). Kaplan-Meier method was used to achieve time to progression (TTP) and overall survival (OS) curves for each group. TTP and OS curves were compared to demonstrate eventual relevant differences between the 2 groups.Seventeen patients underwent (90)Y RE, and one subject was considered ineligible. According to PET Response Criteria in Solid Tumors, partial response was found in 14 patients (82.4\%), stable disease in 3 (17.6\%). No patient showed complete metabolic response. The mean OS for all patients was 64.5±5.0 weeks. Subjects with a ΔTLG>50\% and ΔTLG<50\% had a mean OS of 79.6±3.6 and 43.1±2.0 weeks, respectively (p<0.001). TTP resulted of 28.9±3.8 weeks for the whole cohort. Patients with ΔTLG>50\% had a significantly longer TTP (mean 36.9±3.6 weeks) than those with ΔTLG<50\% (mean 13.7±1.7 weeks, p=0.001).Our results indicate that (90)Y RE can be an effective and safe therapy for ICC. ΔTLG calculated on post-treatment [(18)F] FDG PET-CT agrees with patients' final outcome.