Selective internal radiation therapy (SIRT) of inoperable primary and metastatic hepatic tumors with 90-Yttrium microspheres (SIR-Spheres(R))

1798 Objectives: Since September 2003, we have been treating at our institution irresectable malignant liver tumors with intrahepatic infusion of 90-Yttrium microspheres (either as first-line therapy of after progression to conventional therapies). Our aim was to determine the therapeutic response in terms of local control of the disease, side effects of the treatment, absorbed doses to target organs and tumor, as well as the radiation field around the patient. Methods: 60 patients were treated until November 2005 (26 hepatocellular carcinomas, 12 colorectal ca, 8 neuroendocrine tumors, 6 breast ca, 8 other tumors). Previously, a meticulous evaluation was performed to determine the posibility of secondary pneumonitis after radiospheres infusion, calculate the tumor to non-tumoral liver ratio (T/N), visualize activity in extrahepatic abdominal organs and correlate the vascularization pattern with the lesions distribution (by means of CT or MR). For this purpose, a scintigraphy using Tc-99m labelled Macro-aggregated Albumin injected in the hepatic artery using a trans-femoral catheter was done. After calculating the activity to deliver on the basis of avoiding lung and normal liver damage, microspheres were administrated into the same hepatic artery location as compared with the scintigraphy. Results: All of them are presented as median (range). Tumoral burden in the exposed area: 17.28% (1-98.5). Lung shunting: 6.86% (1.99-25.18). Activity administrated: 1.78 GBq (0.75-3.05). Estimated doses delivered to tumor: 139.68 Gy (22.49-383.60), non-tumoral liver: 34.40 Gy (5.62-100.25) and lungs: 5.96 Gy (1.18-20.59). Patient dose rates at contact: 100 microSv/h (40-220) and at one meter: 2.85 microSv/h (0.3-6.5). In four patients (among the first eighteen treatments) severe side effects were observed (including hepatic encephalopathy, ascites, multiorgan failure). Maximum toxicity in other cases was transient cholestasis. A Kaplan-Meier analysis showed a median time to local progression of 9 months. At the time of maximum follow-up 28 patients (46.7%) were still in local control of the disease. Conclusions: SIRT of hepatic tumors is a new and complex therapeutical tool that requires training and a learning period. It is a safe therapy, but there is a possibility of severe side effects. Therefore, a good selection of patients is mandatory. Due to the heterogeneity of the patients treated (several of them with concomitant chemotherapy) it is difficult to analysed properly the results, but it seems like SIRT could help achieving local control of the disease.