Targeting Accuracy of Image-Guided Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma in Real-Life Clinical Practice: In Vivo Assessment Using Hepatic Parenchymal Changes on Gd-EOB-DTPA-Enhanced Magnetic Resonance Images.

PURPOSE: Stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma (HCC) has emerged as an alternative treatment option when curative treatment modalities cannot be applied. Although excellent local tumor control has been achieved with SBRT, the targeting accuracy in real-life practice remains poorly understood. We proposed an in vivo assessment of targeting accuracy using hepatic parenchymal changes observed on gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) images and applied this method to investigate the "real-life" targeting accuracy of image-guided SBRT.

METHODS AND MATERIALS: We selected 29 patients with available follow-up MR images acquired 2 to 4 months after completion of SBRT. All patients were administered 45 Gy in 3 fractions. The treated HCC and the region of hepatic parenchymal changes in the hepatobiliary phase of MR images were delineated. We evaluated the discrepancies between the center of the HCC and that of the parenchymal change area (intercenter discrepancy [ICD]). We also analyzed the difference in ICDs between those who underwent SBRT with intrahepatic marker guidance and those with diaphragm guidance.

RESULTS: The median ICD in the 3-dimensional direction was 6.81 mm (interquartile range [IQR], 4.27-9.61 mm). Those for the craniocaudal, left-right, and anteroposterior components were 2.70 mm (IQR, 1.83-4.06 mm), 1.63 mm (IQR, 0.76-3.49), and 4.12 mm (IQR, 1.20-6.96 mm), respectively. The median ICD for patients who underwent treatment with intrahepatic marker guidance and those with diaphragm guidance was 7.53 mm (IQR, 6.63-10.86 mm) and 5.60 mm (IQR, 4.28-8.18 mm), respectively. There was no significant difference in ICD between those who underwent treatment with intrahepatic marker guidance and those with diaphragm guidance (P = .296).

CONCLUSIONS: The hepatic parenchymal changes observed on Gd-EOB-DTPA-enhanced MR images can be used to assess the targeting accuracy after SBRT for HCC.