Importance of the field: Metastatic tumours of the liver are responsible for significant morbidity and mortality, and only a small percentage is resectable with curative intent. Hepatic artery radioembolization (RE) with yttrium-90 ((90)Y)-loaded microspheres is an alternative treatment for patients with unresectable primary or secondary liver tumours, especially in cases of metastatic colorectal cancer (mCRC) and hepatocellular carcinoma (HCC).

Areas covered in this review: Data from recent relevant clinical trials with (90)Y-RE are discussed, focusing on response rate assessments and treatment outcome.

What the reader will gain: Current data show that (90)Y-RE combined with radiosensitizing chemotherapy is a safe and efficient modality that extends the time to progression in liver mCRC and unresectable HCC, although no survival benefits have been demonstrated. The treatment response after (90)Y-RE seems to be better assessed using metabolic response assessments with serial fluorodeoxyglucose positron emission tomography (FDG-PET) in cases of FDG-avid tumours than with morphological criteria measured on computed tomography or magnetic resonance imaging (RECIST or WHO trials). Predictive models using multimodality imaging approaches (PET-SPECT-CT image fusion algorithms) have been proposed to better select patients for (90)Y-RE. The optimal routine role of radioembolization remains to be defined; the complexity and wide availability of available therapeutic alternatives confuses the role of a locoregional treatment in a generalized disease.

Take home message: (90)Y-RE is a safe and efficient treatment modality in salvage therapy of colorectal cancer metastatic to the liver and in unresectable HCC. However, it has still to find its place as a first- or second-line treatment of mCRC in combination with or as an alternative to available biological agents. The role of (90)Y-RE in other solid tumour types metastatic to the liver is much more uncertain and investigations in clinical situations in which disease is strictly limited to the liver are required. Pretherapeutic work-up, initially developed to explore hepatic vasculature and to assess lung shunting, might be able to predict treatment outcome, allowing a better patient selection.