Room: AAPM ePoster Library
Purpose: To determine dosimetric parameters associated with volumetric liver changes on MRI and changes in liver function assessed by Albumin-Bilirubin (ALBI) score for patients treated with SBRT for hepatocellular carcinoma (HCC).
Methods: Patients treated with SBRT for HCC with pre- and post-treatment MRI using Gd-EOB-DTPA contrast and minimum 6 months imaging follow-up were included. Whole liver and lobar liver volumes were contoured on pre- and post-SBRT MRI scans using Couinaud classification as right lobe (RL), left lobe (LL), and caudate lobe (CL). ALBI scores were tabulated from SBRT start and up to 2 years post-treatment. Dosimetric data from the SBRT planning CT were overlaid with pre-treatment MRI using contour-based deformable registration, assessed by DICE coefficient.
Results: 53 patients were included with 37.9 months median follow-up. In total, 362 MRI scans were used to assess liver volumes pre- and post-SBRT, median 6 per patient. Baseline median liver, RL, LL and CL volumes were 1454cm3, 1017cm3, 407cm3 and 32cm3, respectively. Median change in liver, RL, LL and CL volume post-SBRT was -7.2%/year, -7.7%/year, -2.8%/year and -8.3%/year, respectively, with LL increasing for some patients. Mean dose and volume receiving 20Gy (V20Gy) were the strongest predictors of volumetric change (Table1 supporting document). Worse baseline ALBI grade was associated with steeper liver volume decrease (p=0.031), whereas rate of worsening ALBI score post-SBRT was associated with mean dose to liver (0.044/month/10Gy, p=0.017), LL (0.023/month/10Gy, p=0.038), CL (0.021/month/10Gy, p=0.015) but not RL (0.017/month/10Gy, p=0.22). Patients with improving vs. worsening post-SBRT ALBI scores received a mean liver dose of 6.9Gy vs. 10.3Gy (p=0.003).
Conclusion: Significant volumetric changes were seen post-SBRT, which correlated with mean dose and V20Gy to the liver and lobes. Most patients (75%) had RL tumors and sparing the LL allowed for some compensatory hypertrophy. Dosimetric parameters were also strongly associated with worsening liver function post-SBRT.