Hepatocellular carcinoma: evaluation of therapeutic response to interventional procedures

Surgical resection remains the principal curative treatment for hepatocellular carcinoma (HCC) [1]. However, most patients with HCC are not eligible for surgical resection at the time of diagnosis owing to the status of the patients or tumors [2, 3]. In the past decade, a variety of interventional procedures have been employed for the local control of HCC. These include transcatheter arterial chemoembolization (TACE) [4], local ablation techniques using a direct intratumoral injection of compounds such as absolute ethanol [5] or hot saline [6], and thermal ablation techniques such as microwave ablation [7] and radiofrequency (RF) ablation [8]. Precise evaluation with imaging modalities is important to determine whether the tumor is completely treated or needs additional treatment. The information provided by imaging studies is used to estimate prognosis and can modify the treatment plan. Color or power Doppler sonography (US), computed tomography (CT), magnetic resonance imaging (MRI), and angiography have been used for that purpose [9–15]. After successful treatment, the treated lesion is devoid of vascularity on color or power Doppler US and it no longer enhances with contrast material on CT and MRI. When the tumor is not completely treated, residual viable tissue can be detected on Doppler US, CT, and MRI as focal hypervascular foci within the treated lesion [9–11, 14, 15]. For the definite assessment of therapeutic efficacy of interventional procedures, histologic examination using percutaneous needle biopsy may be needed. The procedure, however, is invasive and the specimen retrieved does not always represent the entire lesion owing to sampling errors [15]. Therefore, follow-up imaging studies have been used mostly for that purpose. In this article, we review the imaging findings of HCC treated with interventional procedures and discuss the values and pitfalls of each imaging modality in evaluating therapeutic response.