An implantable delivery system includes a macrostructure formed of bioresorbable material selected from a group of alphahydroxy acids and defined to include an internal architecture of intercommunicating void spaces. A first cytotoxic agent in the preferred form of cisplatin is joined to the macrostructure during formation. A microstructure in the preferred form of a blend of high molecular weight hyaluronic acid conjugated with a second cytotoxic agent in the preferred form of paclitaxel and of pure high molecular weight hyaluronic acid is invested in the void spaces. Thus, when implanted, the paclitaxel and cisplatin are released sequentially, each initially at high level concentrations followed by lower release. Radiotherapy can be begun after the release of the paclitaxel has been completed but while the cisplatin is being released.