E1798. Post-Treatment Imaging Findings and Pitfalls of Various Liver Regional Therapies in Patients With Hepatocellular Carcinoma
  1. Steven Lee; University of Los Angeles
  2. Shannon Yoo; University of Los Angeles
  3. Edward Lee; University of Los Angeles
In the last decade, there has been increasing use of locoregional therapies (LRT) for treatment of liver malignancies or liver metastases. Among the primary liver malignancies, hepatocellular carcinoma (HCC) is the most common. Liver transplantation is the gold standard of treatment, but the lack of available livers, socioeconomic factors, and the patient’s specific medical conditions make this option untenable for many. Surgical resection of the malignancy is the next best treatment but is also untenable for many due to their various medical conditions. LRTs such as conventional TACE (cTACE), TACE with drug-eluting beads (DEB-TACE), transarterial radioembolization (TARE), radiofrequency ablation (RFA), and microwave ablation (MWA) are being increasingly used to treat primary liver malignancies such as HCC. However, posttreatment changes from the various LRTs may be difficult to differentiate from a residual or recurrent tumor.

Educational Goals / Teaching Points
This exhibit aims to review the classic CT and MRI findings of HCC, a general overview of the different LRTs used to treat HCC, review post-treatment CT and MR images from the various LRTs, and common imaging pitfalls to be aware of with the various LRTs.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
In cTACE, the residual lipiodol is hyperattenuating on CT, and limits evaluation of an incomplete treatment response. In MRI, the tumor has variable T1- and T2-weighted intensities depending on when the imaged were acquired. In DEB-TACE, the imaging findings are similar to cTACE without the hyperattenuation from the lipiodol. The tumor can appear larger in the first 6 months due to perilesional and perivascular edema. There can also be capsular retraction from tumor necrosis that can distort the liver architecture. RFA and MWA include CT images for post-ablation treatment can be similar to DEB-TACE, with the notable exception that gas bubbles can be present into the hepatic lesion from the hydrogen gas being used for the ablation. The ablated tumor has variable presentation on MRI. Common pitfalls are perilesional hyperenhancement can be seen in the first 3 months posttreatment due to physiologic inflammatory response and be mistakenly identified as a residual tumor. It can be differentiated by the absence of portal venous washout and normally has a circumferential morphology. Arterioportal shunts can develop as a complication to TACE or TARE. They normally present as subcapsular enhancement in the arterial phase but can be differentiated from tumor because shunts are isoattenuating in the portal venous and delayed phases. In ablation treatments, the probe track should be closely monitored due to the risk of tumor cells seeding the track. It should be noted in patients with a history of cTACE and then ablation can scatter the lipiodol throughout the liver parenchyma or even into the peritoneum.

LRTs have various post treatment imaging depending on which LRT is being used. Understanding the different LRTs and the respective post-treatment imaging is needed to be able to identify between an expected post-treatment finding vs residual tumor more accurately in HCC patients.