Efficacy of slow-releasing anticancer drug delivery systems on transplantable osteosarcomas in rats

New drug delivery systems for cis-diamminedichloroplatinum (CDDP) incorporated into vehicles, such as polymethylmethacrylate (PMMA), fibrin glue (F.G.), alpha-tricalciumphosphate (TCP) and ethylenevinyleacetate copolymer (Polymer) were examined using a rat osteosarcoma model. The materials containing CDDP were directly implanted into the tumors or subcutaneous tissue of rats, and the inhibitory effects on tumor growth and lung metastasis were evaluated. Data on in vitro kinetics of CDDP release revealed good results for both TCP and F.G., and the release pattern from TCP to be most appropriate for a slow-releasing drug delivery system. This was supported by the results of the implantation experiments, whereby the direct implantation of TCP containing CDDP (CDDP-TCP) into tumors, gave significantly better inhibitions of tumor growth and metastasis than either non-treatment (P < 0.01) or subcutaneous implantation (P < 0.05). In a second experiment, using different administration procedures, different inhibitory effects on tumor growth and lung metastatic potency were observed with intra-arterial and intravenous CDDP administration, as well as with CDDP-TCP implanted subcutaneously. Suppression effects of CDDP (10 mg/kg)-TCP directly implanted into tumors were equal to those of intra-arterial (2.5 mg/kg) and intravenous (5.0 mg/kg) administrations. The present results suggest CDDP-TCP implantation to be effective as a slow-release drug delivery system for inhibiting tumor growth and metastasis, and that it should be a useful adjuvant to conventional i.v. or i.a. chemotherapy.