Liver-directed intra-arterial
therapies are
palliative treatment options for patients with unresectable
liver cancer; their use has also resulted in patients being downstaged leading to curative resection and
transplantation. These intra-arterial
therapies include transarterial embolization, conventional transarterial chemoembolization (TACE), drug-eluting bead TACE and radioembolization. Assessment of imaging response following these liver-directed intra-arterial
therapies is challenging but pivotal for patient management. Size measurements based on computed tomography or magnetic resonance imaging (MRI) have been traditionally used to assess
tumor response to
therapy. However, these anatomic changes lag behind functional changes and may require months to occur. Further, these intra-arterial
therapies cause acute
tumor necrosis, which may result in a paradoxical increase in
tumor size on early follow-up imaging despite complete cell death or
necrosis. This concept is unique comparing to changes seen following systemic
chemotherapy. The recent development of functional imaging techniques including diffusion-weighted MRI (DW MRI) and positron emission tomography (PET) allow for early assessment of treatment response and even prediction of overall
tumor response to intra-arterial
therapies. Although the results of DW MRI and PET studies are promising, the impact of these imaging modalities to assess treatment response has been limited without standardized protocols. The aim of this review article is to delineate the best practice for assessing
tumor response in patients with primary or secondary hepatic
malignancies undergoing intra-arterial
therapies.