Direct Interstitial Injection: An Approach to Optimizing Therapeutic Ratios for Safe and Effective Delivery of High-dose Radionuclide Therapy in Treating Solid Tumors (P446)
Mon, July 08
Gatlin C/D
Poster Session
Part of:
Poster Session 1
Info
Abstract Text:
The limiting constraint in all modes of radiation therapy is unwanted dose to non-target normal organs and tissues, which can cause severe side-effects. An ideal radionuclide therapy places 100% of the treatment dose uniformly within the clinical target volume without radionuclide out-migration from the tumor. Such treatment can be achieved by employing an optimum radionuclide and chemical form with carrier properties that facilitate injection, placement, and in-tumor retention. An optimized radiation dose achieves effective tumor destruction while preventing or minimizing normal tissue adverse reactions. Yttrium-90 emits no gamma rays and can be handled safely with negligible dose to workers, patients, and family members. Methods: Yttrium-90 was prepared as insoluble (yttrium phosphate) microparticles in a phosphate-buffered saline (PBS) solution mixed with a polymer composite (hydrogel) carrier for direct intra-tumoral injection. Privately owned cats, dogs, and horses presenting with soft-tissue sarcomas were treated at several veterinary clinics to demonstrate safety, best placement methods, and most effective treatment doses. Results: Upon injection using multiple parallel-needles, the carrier solution warmed and gelled in situ--forming a solid matrix that entrapped the Y-90 microparticles and prevented out-migration via blood circulation. Co-registered PET/CT imaging post-injection confirmed uniform placement in target tissues. Each subject exhibited an objective response to therapy; best results were associated with smaller tumors treated at higher doses (300 to 400 Gy). Treated animals experienced no radiation-related illness or adverse tissue reactions. Therapeutic ratios achieved ranged from 200:1 upwards to 10000:1. Complete tumor destruction was confirmed by histopathology. Conclusions: Some tumors represent poor candidates for surgical excision or cannot be treated using external beams for curative therapy. However, direct intra-tumoral injection of Y-90-microparticles in a polymer composite matrix provides a safe, efficient, high-dose therapy, with tumor cell killing associated with localized dose. Results of this research confirm the opportunity for multiple oncology applications in both human and veterinary patients.
Keywords:
radionuclide therapy cancer treatment yttrium-90
Session Topic:
MA5: Radiation Protection in Healthcare
Authors
Darrell R. Fisher, Ph.D.
Versant Medical Physics and Radiation Safety
Michael K. Korenko
