Is one device more effective than the other, with respect to radioembolization for hepatocellular carcinoma with or without portal vein thrombosis, metastatic colorectal cancer and neuroendocrine tumours? Examining the medical literature, the answer is “no”, Robert Lewandowski, Chicago, USA, said.
The most significant studies regarding radioembolization of unresectable hepatocellular carcinoma patients with glass (Salem R et al, Gastroenterology 2010) or resin (Sangro et al, Hepatology 2011) microspheres demonstrate comparable clinical outcomes, he noted. The same can be said when studying the clinical outcomes of radiomebolization for patients with metastatic colon cancer in the palliative setting. Lewandowski used two studies to highlight this fact (Mulcahy et al, Cancer 2009 and Kennedy et al, IJRBP 2006). He pointed out another study that compared glass and resin microspheres in this arena, treating 27 patients with glass microspheres and 19 patients with resin microspheres (Wong et al, 2006, Cancer Biotherm Radiopharma). While there was a significant mean reduction in tumour load based on PET imaging, this was irrespective of the agent used. There was no difference in mean percentage reduction of tumour metabolism between the two devices. For metastatic neuroendocrine tumours, the only study to compare both devices (Rhee et al, Annals of Surgery 2008) demonstrated very similar response rates at six months for glass (92% partial response or stable disease) and resin (94% partial response or stable disease) microspheres, according to the response evaluation criteria in solid tumours classification. The median survival was 22 months with glass and 28 months with resin (p=0.82) microspheres.
While there is no difference in clinical outcomes between the radioembolic devices, there are physical differences between them. While resin microspheres are more embolic, glass microspheres are heavier and hotter. These physical differences do not appear to have adverse clinical sequelae, he said. Lewandowski also stated that there were no well-designed, controlled studies suggesting that the occurrence of radiation-induced liver disease (i.e., liver failure occurring within 90 days of treatment, or liver failure after day 90 without tumour progression) or gastrointestinal ulcers secondary to non-target embolization is higher with one device over another.
The delivery systems for the radioembolic devices do take into account the physical differences between the devices. Dosimetry for glass microspheres uses the targeted volume of perfusion. The microspheres are delivered in the requested activity and are administered via saline infusion. No imaging is required during administration as the entire dose is typically delivered in the first few milliliters. With resin microspheres, dosimetry is based on body surface area and tumour burden. A technologist is responsible for drawing up the desired dose from a standard dose vial. The microspheres are administered via sterile water under intermittent fluoroscopy. The dose is typically delivered in small aliquots over 20 minutes. Lewandowski emphasised the importance of recognising and understanding the differences between these two devices in order to optimise Y90 administration.