Radiation lobectomy: Time-dependent analysis of future liver remnant volume in unresectable liver cancer as a bridge to resection

Background & Aims Portal vein embolization (PVE) is a standard technique for patients not amenable to liver resection due to small future liver remnant ratio (FLR). Radiation lobectomy (RL) with ⁹⁰Y-loaded microspheres (Y90) is hypothesized to induce comparable volumetric changes in liver lobes, while potentially controlling the liver tumor and limiting tumor progression in the untreated lobe. We aimed at testing this concept by performing a comprehensive time-dependent analysis of liver volumes following radioembolization. Methods 83 patients with right unilobar disease with hepatocellular carcinoma (HCC; N = 67), cholangiocarcinoma (CC; N = 8) or colorectal cancer (CRC; N = 8) were treated by Y90 RL. The total liver volume, lobar (parenchymal) and tumor volumes, FLR and percentage of FLR hypertrophy from baseline (%FLR hypertrophy) were assessed on pre- and post-Y90 CT/MRI scans in a dynamic fashion. Results Right lobe atrophy (p = 0.003), left lobe hypertrophy (p <0.001), and FLR hypertrophy (p <0.001) were observed 1 month after Y90 and this was consistent at all follow-up time points. Median %FLR hypertrophy reached 45% (5-186) after 9 months (p <0.001). The median maximal %FLR hypertrophy was 26% (-14→86). Portal vein thrombosis was correlated to %FLR hypertrophy (p = 0.02). Median Child-Pugh score worsening (6→7) was seen at 1 to 3 months (p = 0.03) and 3 to 6 months (p = 0.05) after treatment. Five patients underwent successful right lobectomy (HCC N = 3, CRC N = 1, CC N = 1) and 6 HCCs were transplanted. Conclusions Radiation lobectomy by Y90 is a safe and effective technique to hypertrophy the FLR. Volumetric changes are comparable (albeit slightly slower) to PVE while the right lobe tumor is treated synchronously. This novel technique is of particular interest in the bridge-to-resection setting.