A spacer for use in brachytherapy, and radiotherapy, is formed of an encapsulating material in a generally cylindrical or elongated shape. Regions are formed within the spacer and retaining therapeutic loads, such as radiation sources and/or pharmaceutical therapeutic loads, and/or any other substances to treat a patient, such as drug liquids, powder or particles (e.g., microparticles or nanoparticles), with the particles or powders combined with binders, such as polyacrylamide, that are selected to gradually disperse the powder or particles at a desired rate. Such regions can be formed at various locations within the spacer, and can have various shapes depending on the particular design and intended usage. The outer surface of the encapsulating material can optionally include one or more fins, ribs or other physical protuberances or features that improve the fixity of the spacer when implanted within a patient's body.