A device having a biocompatible polymer as a body and regularly spaced radiation seeds and regularly spaced magnetic materials disposed of within the body of the biocompatible polymer, or uniformly distributed liquid radiation and magnetic fluid materials within a polymer slab, hollow thick wall polymer shell, or thin wall polymer balloon, as suitable for surgical placement within a resection cavity for treatment of at-risk tissue in the tumor margin with local hyperthermia in combination with radiation and potentially also with chemotherapy and/or immunotherapy that is slowly released from the biocompatible polymer.
