Selective Internal Radiotherapy in Liver Tumors: Early Promise Yet to be Fulfilled

Selective intra-arterial radiotherapy (SIRT) is a technique which has evolved over the past 30 years. In present this is primarily used to treat primary and secondary tumors in the liver. The technique normally depends on the delivery of a therapeutic radiopharmaceutical or radiolabeled particulate via a radiologically placed intra-arterial catheter in the hepatic artery. This is because most of these tumors have a single arterial blood supply but normal hepatocytes are supplied by both the hepatic artery and portal vein. Initially, this was done with I-131 labelled poppy seed oil but this technique was only used in a few centers. The technique became more popular when Y-90 particulates become widely available. Early results were promising but in phase 3 randomized controlled trials resulted in disappointing results compared to systemic chemotherapy. More recent work however, have shown that increasing the radiation dose to the tumor to at least 60Gy and combining with more effective systemic therapies are starting to produce better clinical results. There have also been advances in the angiographic methods used to make this into a day-case technique and the use of new radionuclides such as Ho-166 and Re-188 provides a wider range of possible SIRT techniques.