Purpose: Glioblastoma multiforme is an aggressive brain tumor that generally recurs locally and has a dismal median survival < 18 months. In vivo studies have shown that thermal enhancement ratio (TER) of up to 5 can be achieved when hyperthermia and radiation are applied simultaneously, which is not currently possible. The goal of this project is to develop a novel thermobrachytherapy (TBT) balloon implant to accomplish this. Our phase I development has 3 specific aims: i) to fabricate TBT balloons; ii) to evaluate the device for compatibility of hyperthermia and HDR and to characterize thermal and radiation dosimetry in laboratory studies; and iii) to characterize heating patterns in perfused brain tissue via in vivo animal studies and to evaluate reliability and heating performance.
Methods: The TBT balloon has two layers: an inner layer filled with saline to expand the resection cavity into approximately spherical shape, and an outer layer filled with magnetic nanoparticle (MNP) solution that absorbs energy from an external magnetic field to generate heat. The balloon is connected to a shaft that houses 4 ports to fill inner and outer layers, insert an HDR source into the balloon center and a fiberoptic sensor into the outer balloon for temperature monitoring. Five TBT balloons were fabricated. Gafchromic film was used to determine HDR dwell position to achieve radiation dose distribution centered at the balloon center. Optically stimulated luminescent dosimeters were used to measure radiation dose.
Results: The presence of MNP, a 133 kHz magnetic field, and 43-55°C heating did not affect radiation dose significantly. Thermal mapping demonstrated spherically symmetric heating in phantom and will continue in vivo.
Conclusion: Novel dual-modality balloons have been fabricated and tested in the lab. Because of the positive lab results, we will continue with in vivo dosimetry in preparation for phase II clinical development.
Funding Support, Disclosures, and Conflict of Interest: NIH R41 CA-239815
Not Applicable / None Entered.