Compensatory hypertrophy of the liver after external beam radiotherapy for primary liver cancer

Purpose We investigated whether external beam radiotherapy (EBRT) could induce compensatory liver hypertrophy in liver cancers and assessed related clinical factors. Methods A total of 82 consecutive patients receiving EBRT for hepatocellular carcinoma (n=77) or cholangiocarcinoma (n=5) from April 2012 to June 2014 were recruited and divided into two subgroups according to tumor location in the right or left lobe. The left lateral and right lobes were considered as unirradiated volumes accordingly. Total liver volume (TLV), nontumor liver volume (NLV), left and right lobe whole volume (LLWV and RLWV, respectively), volume of liver irradiated< 30Gy (V-< 30Gy), Child-Pugh (CPS) score, future liver remnant (FLR) ratio, and percentage of FLR hypertrophy from baseline (%FLR) were assessed. Results In the right lobe group, %FLR hypertrophy and LLWV increased significantly at all follow-ups (p<0.001). %FLR hypertrophy steadily increased until the fourth follow-up. Multivariate analysis showed that the factor associated with maximum %FLR hypertrophy was tumor extent (upper or lower lobe vs. both lobes; p=0.022). Post-RT treatments including transarterial chemoembolization or hepatic arterial infusion chemotherapy were associated with a CPS increase >= 2 (p=0.002). Analysis of the RT only subgroup also showed a significant increase of %FLR until the fourth follow-up (p<0.001). In the left lobe group, %FLR hypertrophy and RLWV showed no significant changes during follow-up. Conclusion Significant compensatory hypertrophy of the liver was observed, with a steady increase of %FLR hypertrophy until the fourth follow-up (median: 396 days). Locally advanced tumors extending across the upper and lower right lobe were a significant factor for compensating hypertrophy after EBRT.