Biological In Situ Dose Painting For Image-Guided Radiation Therapy Using Drug-Loaded
Implantable Devices (BIS-IGRT)
Implantable devices routinely used for increasing spatial accuracy in modern image-guided
radiation treatments (IGRT), 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 versus eluter
size and drug prop- erties were tabulated. Four radiosensitizer-loaded ﬁducials
provide adequate radiosensitization for 4-cm-diame- ter lung tumors, thus potentially
boosting biologically equivalent doses in centrally located stereotactic body treated
lesions. Similarly, multiple drug-loaded spacers provide prostate brachytherapy
with ﬂexible shaping of ‘‘biologi- cally equivalent doses’’ to ﬁt requirements difﬁcult
tomeet by using radiation alone, e.g., boosting a high-risk region juxtaposed to
the urethra while respecting normal tissue tolerance of both the urethra and the
rectum. Drug loading of implantable devices routinely used in IGRT provides new
opportunities for therapy modulation via biological in situ dose painting.