Therapy Planning with SPECT/CT in Radioembolization of Liver Tumours

Abstract

Radioembolisation (RE) with yttrium-90 (⁹⁰Y) microspheres, also named selective internal radiation therapy (SIRT), is a promising catheter-based liver-directed modality for patients with primary and metastatic liver cancer. RE provides several advantages over traditional treatment methods including its low toxicity profile (Campbell et al., Phys Med Biol 45:1023–1033, 2000; Salem and Thurston, J Vasc Interv Radiol 17:1251–1278, 2006). Its rationale arises from the anatomic and physiological aspects of hepatic tumours being exploited for the delivery of therapeutic agents. The prominent feature is the dual blood supply of liver tissue from the hepatic artery and the portal vein. Approximately 60–80% of hepatic blood is derived from the gastrointestinal (GI) tract via the portal vein and 20–40% from the systemic circulation via the hepatic artery (Lien and Ackerman, Surgery 68:334–340, 1970). Observations on vascular supply to hepatic malignancies have demonstrated that metastatic hepatic tumours measuring >3 mm derive 80–100% of their blood supply from the arterial rather than the portal hepatic circulation (Lien and Ackerman, Surgery 68:334–340, 1970). ⁹⁰Y is a pure β-emitter, produced by neutron bombardment of ⁸⁹Y in a reactor, with a limited tissue penetration (mean 2.5 mm, max 11 mm) and a short half-life of 64.2 h, making it an ideal transarterial liver-directed agent (Ahmadzadehfar et al., Semin Nucl Med 40:105–121, 2010). Two ⁹⁰Y microsphere products are commercially available: TheraSphere^® (glass microspheres) and Sir-sphere^® (resin microspheres). There are some distinct differences in properties between the two products discussed in detail elsewhere (Ahmadzadehfar et al., Semin Nucl Med 40:105–121, 2010). In the selection process of patients referred for RE, several aspects should be considered. Patients selected for RE should have (1) unresectable hepatic primary or metastatic cancer, (2) liver-dominant disease, (3) a life expectancy of at least 3 months and (4) an ECOG performance score of ≤2 as well as a preserved liver function (Kennedy et al., Int J Radiat Oncol Biol Phys 68:13–23, 2007). Overall, the incidence of complications of RE of the liver malignancies for appropriately selected patients and accurately targeted delivery is very low (Murthy et al., Radiographics 25(Suppl 1):S41–S55, 2005). Serious complications have been reported when microspheres were inadvertently deposited in excessive amounts in organs other than liver or when the liver received more radiation than its tolerance, which is called radioembolisation-induced liver disease (REILD) (Riaz et al., J Vasc Interv Radiol 20:1121–1130, 2009). Radiation and diminished blood supply due to embolisation by the spheres and subsequent hypoxia may result in ulceration and even perforation of the stomach and duodenum (Riaz et al., J Vasc Interv Radiol 20:1121–1130, 2009; Yip et al., J Gastroenterol Hepatol 19:347–349, 2004). ⁹⁰Y-induced ulceration of the stomach or duodenum can be resistant to medical therapy and surgery may be required (Carretero et al., Am J Gastroenterol 102:1216–1220, 2007). Reported complications include gastrointestinal ulceration/bleeding, gastritis/duodenitis, cholecystitis, pancreatitis, radiation pneumonitis and hepatic decompensation (Salem and Thurston, J Vasc Interv Radiol 17:1251–1278, 2006; Kennedy et al., Int J Radiat Oncol Biol Phys 68:13–23, 2007; Riaz et al., J Vasc Interv Radiol 20:1121–1130, 2009; Yip et al., J Gastroenterol Hepatol 19:347–349, 2004; Carretero et al., Am J Gastroenterol 102:1216–1220, 2007; Leung et al., Int J Radiat Oncol Biol Phys 33:919–924, 1995; Murthy et al., J Vasc Interv Radiol 18:553–562, 2007; Salem et al., Am J Clin Oncol 31:431–438, 2008; Atassi et al., J Vasc Interv Radiol 19:691–697, 2008).