Compensatory Hepatic Hypertrophy After Carbon Ion Radiotherapy for Hepatocellular Carcinoma: Factors Associated With Its Development and Relationship With Prognosis

ABSTRACT Aims This study aimed to investigate predictors of compensatory hepatic hypertrophy and their association with prognosis in patients undergoing carbon ion radiotherapy (CIRT). Methods In this retrospective analysis, we included 94 patients with hepatocellular carcinoma (HCC) who received CIRT at Gunma University between November 2010 and June 2020. Significant compensatory hypertrophy was defined as an increase of more than 50 cm 3 in the hepatic lateral segment volume at 3 months after CIRT. Results The median age of the patients was 76.5 years (IQR, 69.0–83.0), and 63 (67.0%) were male. The median volume of the lateral segment was 254 cm 3 (IQR, 183–354), and the median clinical target volume (CTV) was 72.52 cm 3 (IQR, 33.69–148.75). Compared with pretreatment values, an increase in volume was observed in 74 (78.7%) patients, whereas a decrease was noted in 20 (21.3%). Significant compensatory hypertrophy was observed in 27 (28.7%) patients. Patients with significant compensatory hypertrophy had larger tumor diameters and CTV values than those without hypertrophy ( p = 0.03 and p = 0.01, respectively). The median overall survival was 87.3 months in patients with significant compensatory hypertrophy and 88.8 months in those without, with no significant difference between the groups ( p = 0.5). In contrast, patients without worsening ALBI scores had significantly better survival than those with worsening ALBI scores ( p = 0.004). Conclusions Compensatory hypertrophy was frequently observed after CIRT in HCC patients but was not associated with prognosis. Preservation of liver function appears to be important for achieving a favorable prognosis.