RFA Lowers IDO Activity and Slows Non-Ablated Lesion Growth in Multifocal Hepatic Carcinoma

Abstract Background: The aim of this study was to determine whether radiofrequency ablation (RFA) could activate immunity and slow non-ablated lesion growth in multifocal hepatic carcinoma.Methods: We performed a retrospective study on patients with multifocal hepatic carcinoma and assessed the non-ablated lesion growth rate between patients who received RFA and those who did not. In self-controlled study, before and three weeks after RFA, blood samples were collected from patients who received RFA to allow for comparisons of the alpha-fetoprotein (AFP) level, indoleamine 2,3-dioxygenase (IDO) concentration as assessed by enzyme-linked immunosorbent assay (ELISA) and IDO activity as assessed by high-performance liquid chromatography (HPLC).Results: A total of 66 patients were included in the retrospective analysis: there were 46 (69.7%) patients in the treatment group and 20 (30.3%) patients in the control group. The mean growth rate of non-ablated tumors was 0.0291 ± 0.0965 mm/d in the treatment group and 0.0947 ± 0.0754 mm/d in the control group (P = 0.001). The mean concentrations of IDO before and after RFA were 15.57±4.06 ng/ml and 7.53±1.56 ng/ml in 45 eligible patients, and this difference was significant (P = 0.034). The mean IDO activity values were 29.7±22.03 and 25.25±1.75 before and after RFA, respectively (P = 0.031). AFP decreased significantly after RFA, but there was no significant correlation between the decrease in AFP and the decrease in IDO concentration and activity.Conclusions: RFA may induce abscopal effects in hepatic carcinoma patients, manifested by a decrease in IDO concentration and activity and a slowed growth rate in non-ablated lesions.