Stereotactic body radiation therapy of liver tumors: post-treatment appearances and evaluation of treatment response: a pictorial review

Abstract

Stereotactic body radiation therapy (SBRT) is a noninvasive treatment technique for selected patients with primary liver tumors and liver-confined oligometastatic disease. Recently, SBRT has emerged as an alternative treatment option in non-surgical candidates and in whom percutaneous treatment methods are not possible or contraindicated. The experience with SBRT continues to grow. There are currently no imaging guidelines for assessment of tumor response and follow-up schedule following SBRT. SBRT produces characteristic radiation-induced changes in the treated tumor and surrounding liver parenchyma. Knowledge of these changes is essential in the interpretation of follow-up imaging and assessment of treatment response. In this review, we will describe the CT, MRI, and PET imaging findings following SBRT of both the targeted liver tumor and surrounding hepatic parenchyma.

Magnetic Resonance Imaging Evaluation of Hepatocellular Carcinoma Treated With Stereotactic Body Radiation Therapy: Long Term Imaging Follow-Up

“…In the veno-occlusive zone, there was injury to the venule endothelial cells resulting in activation of the clotting cascade, with fibrin deposition and sinusoidal congestion. A recent study by Haddad et al [40] confirmed this pattern of histopathologic findings. Our analysis fits this proposed histologic picture, as HCC treated with SBRT can be persistently hyperenhancing on arterial phase, which could be explained by the giant cell reaction induced by radiation therapy; a finding which would result in arterial phase hyperenhancement.…”

“…Furthermore, the progressive loss of arterial phase hyperenhancment over time may be secondary to progressive cell death, coagulation necrosis and fibrosis induced by the targeted radiation. [40]…”

Evaluation of Hepatic Toxicity after Repeated Stereotactic Body Radiation Therapy for Recurrent Hepatocellular Carcinoma using Deformable Image Registration

“…However, there was no grade 3 or higher biliary stricture, and only six patients had grade 1 mild dilation of the bile duct without significant bilirubin elevation or the need for endoscopic intervention. In addition, the irradiated liver showed focal atrophy in almost all patients, a previously well-known image finding 32 . Additional atrophy was observed with repeated SBRT, but other findings, such as distortion of vascular structure or biliary stricture, were not observed in the overlapping high-dose area.…”

Stereotactic ablative radiotherapy for hepatocellular carcinoma: History, current status, and opportunities

“…Thus, both tumor and normal tissue responses, including possible vascular and biliary duct damage, are expected to manifest quickly, both radiographically and clinically. Manifestation of the effects of radiation on tumors and normal tissues tends to evolve over a more protracted time course . In particular, the posttreatment radiographic appearance of treated liver and liver tumors, including enhancement patterns, change over time.…”

“…Manifestation of the effects of radiation on tumors and normal tissues tends to evolve over a more protracted time course. (41,42) In particular, the posttreatment radiographic appearance of treated liver and liver tumors, including enhancement patterns, change over time. Thus, local control of treated lesions needs to be assessed over serial time points.…”