Biological in-situ dose-painting for image-guided radiation therapy using drug-loaded implantable devices
Robert Cormack, Srinivas Sridhar, W. Warren Suh, Anthony V. D'Amico, and G. Mike Makrigiorgos
Implantable devices routinely used for increasing spatial accuracy in modern image-guided radiation treatments, such as fiducials or brachytherapy spacers, encompass the potential for in situ release of biologically-active drugs, providing an opportunity to enhance the therapeutic ratio. We model this new approach for two types of treatment. Drug distributions from three-dimensional arrangements of drug-eluters were tabulated versus eluter size and drug properties. Four regularly-spaced taxotere-loaded fiducials may provide adequate radio-sensitization for ~4 cm diameter lung tumors, thus potentially boosting biologically equivalent doses in centrally-located SBRT-treated lesions difficult to treat with radiation alone. Similarly, strategic placement of multiple drug-loaded spacers provide prostate brachytherapy with flexible shaping of 'biologically-equivalent doses' to fit requirements that are difficult to meet by using radiation alone, e.g. boosting a high-risk region juxtaposed to the urethra, while respecting the normal tissue tolerance of both urethra and rectum.