Author: Wesley A. Belcher, Robert A. Corns, Jae Won Jung, Matthew S Peach, Swarup Sharma 👨🔬
Affiliation: The University of North Carolina at Chapel Hill, East Carolina University Brody School of Medicine 🌍
Purpose: GammaTiles are a novel intracranial brachytherapy approach designed to directly deliver radiation therapy to residual or recurrent brain tumors following resection. Despite their promising therapeutic benefits, GammaTile migration post-implantation is not well detailed, potentially impacting dose distribution and clinical outcomes. This study uses retrospective image analyses to evaluate the characteristics of GammaTile migration during external beam therapy following implantation.
Methods: Five glioblastoma patients treated with external beam radiation therapy (EBRT) after GammaTile implantation were reviewed to assess migration quantity, patient outcomes and associated risk factors. Two CBCT image sets per patient were acquired after the treatment on Day 1 and Day 23, and the seeds and tiles were manually identified to determine the positional changes. A Kabsch algorithm was used to compute the rotation and translation of all seeds between Day 1 and Day 23 of EBRT (approximately 5.5 weeks). A convex hull was obtained to determine the changes in enclosed volumes.
Results: Between Day 1 and Day 23, the patients' mean seed displacement was 3.5 mm, with a maximum of 8.4 mm. The mean and maximum rotation angles were 3.7 and 5.8 degrees. The mean and minimum changes in the enclosed volume of the seeds were 27% and 16% reduction, respectively.
Conclusion: These findings underscore the importance of understanding GammaTile migration dynamics to improve clinical protocols and outcomes for patients undergoing intracranial brachytherapy. Migration may result in dose heterogeneities, potentially under-dose target regions, and over-dosing surrounding healthy tissues.