Alexander Lam, MD, Megha Nayyar, BS, Chandana Lall, MD; UCI Medical Center
Hepatocellular carcinoma (HCC) is a growing cause of mortality throughout the United States, despite advancements in diagnosis and treatment. As advanced HCC progresses, it becomes more dependent on arterial blood. This translates to the typical imaging characteristics of sharp contrast enhancement during arterial phase, followed by brisk portal venous washout on multiphasic computed tomography (CT). Liver-directed therapies, such as transarterial chemoembolization (TACE), have utilized this preferential arterial flow to administer targeted chemotherapy agents and embolize parasitized arterial branches.
By compromising arterial flow, these embolic therapies alter the imaging characteristics that are typically dependent on hemodynamics, such as multiphasic CT. We hypothesize that the portal venous supply to the tumor experiences a sustained, compensatory increase following chemoembolization, resulting in increased enhancement on portal venous phase when compared with the pretreatment tumor bed. To evaluate this hypothesis, the images of 102 patients with advanced HCC were retrospectively reviewed by two fellowship-trained radiologists. Appropriate preprocedural and posttreatment CT images were performed at noncontrast, arterial, and portal venous phases. Digital subtraction angiographic images were reviewed to confirm the target lesion for evaluation and ensure adequate obliteration of the arterial vessels feeding the tumor. Degree of enhancement was quantified by drawing a circular region of interest (ROI) within the lesion margin of at least 1 cm2. Differences in attenuation of the tumor bed were standardized against normal liver parenchyma and underlying background on the same slice. Enhancement was defined as a difference greater than 15 Hounsfield units (HU) from baseline attenuation on the noncontrast study. Enhancement patterns among the phases were compared between the pre- and posttreatment scans.
A total of 50% (51 out of 102) of HCC cases following TACE demonstrated definite increased enhancement on venous phase compared with the preprocedural images, of which the majority consisted of increased peripheral enhancement. Arterial enhancement was decreased or unchanged for these patients. Also, 24% of cases (25 patients) showed unchanged enhancement on arterial phase images following TACE therapy, with no change in the appropriate venous washout. A total of 11% of cases (11 patients) showed unchanged enhancement on both arterial and portal venous phase after therapy, and 15% of cases (15 patients) demonstrated increased enhancement on arterial phase and not on venous phase.
The majority of cases exhibited increased enhancement on portal venous phase following treatment with TACE, demonstrating the importance of surveillance with proper multiphase imaging to assess for recurrence, especially in light of a decrease in arterial phase enhancement following treatment.
Proceedings of the 97th Annual Meeting of the American Radium Society — americanradiumsociety.org