Learning objectives
To describe the key issues, technique and problems encountered in the work up for appropriateness of Yttrium 90 (Y90) - labeled microsphere selective internal radiation therapy for hepatic primary and secondary malignancies.
Background
Intraarterial Y90-labeled microsphere embolotherapy is an alternative treatment option for patients with multicentric or otherwise unresectable hepatocellular carcinoma, or metastatic disease confined to the liver that does not respond to usual chemotherapy regimes. In our institution, we have been performing this therapy using Y90-labeled resin microspheres (SIRsphere, Sirtex Medical Limited, Lane Cove NSW, Australia) since 2000.
Imaging findings OR Procedure details
Hepatic angiography is used to assess for hypervascularity of the tumours and the anatomy of arterial supply to the liver and surrounding organs. Mulitslice computed tomography (CT) is used to calculate lung, liver and tumour volumes (5mm slices, arterial phase or CT hepatic angiography (CTHA) and portal venous phases), and also to assess for metastatic disease beyond the liver. Technetium-99m-macroaggregated albumin, (TcMAA, LyoMAA, Tyco Healthcare, USA) has a similar particle size to SIR spheres, and can be both imaged and quantified. 110MBq of this tracer is injected into the hepatic artery within the tumour, to exclude significant lung shunting, and to calculate the ratio of radiotracer distribution between the tumour and normal liver. Since 2000, 112 patients have been worked up in our institution, and 60 patients have been treated. The remaining 52 were not treated, due to either significant lung shunting or low tumour to normal liver ratio. In order to improve tumour volumetric quantitation, our work up protocol has evolved to include all three modalities being performed in one visit, with detailed angiographic evaluation of the supply to the liver, stomach, duodenum, pancreas and gallbladder, and often superselective delivery of the TcMAA to the left and right lobes of hte liver separately. Problems we have encountered include a wide variety of arterial anatomy, volumetry and colocalisation issues, and logistics in coordinating between the many services involved (Gastrohepatology, Hepatobiliary surgery, Medical Oncology, Angiography, CT, Nuclear medicine and our SIR sphere suppioer). Overall, this process has prolems has resulted in coordination, more confidence in tumour calculation, time to calculate doses and more timely delivery of the treatment. For many patients this entire process from presentation to treatment has shortened from 3 to 4 weeks to less than 10 days.
Conclusion
Patients can get the Y90 Sirsphere work up performed in one visit, resulting in improved precision of dose calculation and treatment delivery.