2030 - Practice Patterns in Imaging, Contouring and Dosimetric Reporting for Intracranial Brachytherapy Using Collagen-Based Cs-131: Results from a U.S. Multi-Center Survey
Presenter(s)
V. Chaswal1, M. J. Rivard2, K. Rasmussen3, H. Zhang4, D. J. Scanderbeg5, W. Belcher6, R. K. Badkul7, S. Prajapati8, T. K. Podder9, G. Weber10, G. Burkholder10, W. Feng11, R. Kudchadker12, A. Damanto13, R. P. Tolakanahalli14, and C. Ferreira15; 1Miami Cancer Institute, Baptist Health South Florida, Miami, FL, 2Brown University, Providence, RI, 3Department of Radiation Oncology, Mays Cancer Center, UT Health San Antonio, San Antonio, TX, 4Department of Radiation Oncology, University of Southern California, Los Angeles, CA, 5University of California, San Diego, La Jolla, CA, 6Department of Radiation Oncology, Brody School of Medicine, East Carolina University, Greenville, NC, 7University of Kansas Medical Center, Kansas City, KS, 8Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 9SUNY Upstate Medical University, Syracuse, NY, 10University of Minnesota, Minneapolis, MN, 11Bayhealth Medical Center, New york, NY, 12MD Anderson Cancer Center, Houston, TX, 13Memorial Sloan Ketterin Cancer Center, New, NY, 14Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL, 15Department of Radiation Oncology, University of Minnesota Medical School, Minneapolis, MN
Purpose/Objective(s): As clinical adoption of intracranial brachytherapy (ICBT) expands via surgically targeted radiation therapy (STaRT) with Cs-131 embedded in collagen-tiles, substantial variability in treatment planning and evaluation may limit treatment assessment and inter-institutional outcome comparability. This study characterizes current imaging, contouring, and dosimetric reporting practices among centers and identify priority targets for minimum reporting standards.
Materials/Methods: Twelve centers with established STaRT approach for ICBT completed an anonymous comprehensive survey (55 primary questions; >100 sub-items). For this analysis, responses related to pre/post operative imaging requirements, post-implant contouring, target and margin definitions, dosimetric end points, and post-planning quality assurance were analyzed descriptively.
Results: The most commonly treated diagnoses were recurrent metastases (92% of centers), recurrent glioblastoma (83%), recurrent meningiomas (75%), newly diagnosed metastases (67%), and newly diagnosed glioblastoma (50%). Pre-operative imaging practices demonstrated substantial variability. While MRI was universally used, only 50.0% of centers required specific MRI sequence types, most commonly T1-weighted imaging, and 41.7% mandated slice thicknesses of 1–2 mm. Acceptable pre-operative MRI validity windows for tile estimation ranged from 7 to 30 days. Post-implant resection cavity contouring was consistent (83.3%); however, contour delineation methods, post-operative imaging modality selection (MRI versus CT), and naming conventions varied across institutions. Target volumes were contoured by 83.3% of centers, with variability in margin application (0–5 mm) and inclusion of residual enhancing disease by 33.3%. Dosimetric reporting showed partial convergence around minimum target-volume metrics (V100, D90), whereas organs-at-risk contouring and DVH reporting were not universal and varied across centers. Secondary independent treatment planning system dose verification was infrequently performed (16.7%).
Conclusion: Cs-131 collagen-tiles based STaRT approach for ICBT programs demonstrate consistent use of postoperative imaging and cavity-based evaluation; however, key components that determine post-implant dose reporting- imaging timing and protocols, target and margin definitions, dosimetric end-points showed substantial inter-institutional variability. These multi-institutional findings delineate current practice patterns and support the development of standardized guidelines for reproducibility and meaningful comparison for registries and trials in ICBT.