an implantable device that includes at least one sealed chamber containing any of a variety of therapeutic or cytotoxic agents is described . the device is implanted into the patient at one or more sited requiring treatment , e . g ., at several sites within a tumor . once the device is implanted in the patient , the chamber retains its contents until a bioresorbable element of the chamber dissolves , creating an opening through which the agent migrates out of the chamber and enters the body . the bioresorbable element can be simply a plug seal in a plastic or metal chamber . alternatively , all or part of the chamber itself can be formed of a bioresorbable material . the agent can be chemical or biological .