A flexible or elastic brachytherapy strand that includes an imaging marker and/or a therapeutic, diagnostic or prophylactic agent such as a drug in a biocompatible carrier that can be delivered to a subject upon implantation into the subject through the bore of a brachytherapy implantation needle has been developed. Strands can be formed as chains or continuous arrays of seeds up to 50 centimeters or more, with or without spacer material, flaccid, rigid, or flexible.