An analytic dosimetry study for the use of radionuclide-liposome conjugates in internal radiotherapy

A dosimetric analysis has been performed to evaluate the po-tential of liposome systems as carriers of radionuclides in inter-nal radiotherapy. Methods: Pharmacokinetic data for a variety of liposome constructs (multilamellar vesicles [MLV]; small unilamellar vesicles [SUV]; and sterically stabilized liposomes, monosialoganglioside [GM1]-coated) were used to obtain tumor and normal-organ absorbed dose estimates for 67Cu, 188Re, 90Y, and 131I. Dosimetry was performed for two tumor models: sub-cutaneous Ehrlich ascites tumor, growing intramuscularly, and C26 colon carcinoma, growing intrahepatically. Dose estimates were obtained using the MIRD schema. Tumor doses were obtained assuming local deposition of electron energy; photon contributions were incorporated assuming spheric tumor geom-etry. With the conservative assumption that intravenously ad-ministered liposomes achieve rapid equilibration with the re