Outcome of Adult Brain Tumor Consortium (ABTC) prospective dose-finding trials of I-125 balloon brachytherapy in high-grade gliomas: challenges in clinical trial design and technology development when MRI treatment effect and recurrence appear similar.

• Authors: L.R. Kleinberg, Johns Hopkins University; V. Stieber, Piedmont Radiation Oncology; T. Mikkelsen, Henry Ford Hospital; K. Judy, Thomas Jefferson University; J. Weingart, Johns Hopkins University; G. Barnett, Cleveland Clinic; Jeffrey Olson, Emory University; S. Desideri, Johns Hopkins University; X. Ye, Johns Hopkins University; S. Grossman, Johns Hopkins University
• Journal Title: Journal of Radiation Oncology
• Volume: Volume 4, Number 3
• Publisher: Springer Verlag (Germany) | 2015-09, Pages 235-241
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1007/s13566-015-0210-y
• Subjects: Health Sciences, Oncology; Health Sciences, Pharmacology
• Keywords: Brachytherapy; Glioblastoma; Glioma; I-125; Radiotherapy

Abstract

OBJECTIVES: The aim of this study is to define the maximal safe radiation dose to guide further study of the GliaSite balloon brachytherapy (GSBT) system in untreated newly diagnosed glioblastoma (NEW-GBM) and recurrent high-grade glioma (REC-HGG). GBST is a balloon placed in the resection cavity and later filled through a subcutaneous port with liquid I-125 Iotrex, providing radiation doses that diminish uniformly with distance from the balloon surface. METHODS: The Adult Brain Tumor Consortium initiated prospective dose-finding studies to determine maximum tolerated dose in NEW-GBM treated before standard RT or after surgery for REC-HGG. Patients were inevaluable if there was progression before the 90-day posttreatment toxicity evaluation point. RESULTS: Ten NEW-GBM patients had the balloon placed, and 2/10 reached the 90 day timepoint. Five REC-HGG enrolled and two were assessable at the 90-day evaluation endpoint. Imaging progression occurred before 90-day evaluation in 7/12 treated patients. The trials were closed as too few patients were assessable to allow dose escalation, although no dose-limiting toxicities (DLTs) were observed. Median survival from treatment was 15.3 months (95 % CI 7.1-23.6) for NEW-GBM and 12.8 months (95 % CI 4.2-20.9) for REC-HGG. CONCLUSION: These trials failed to determine a maximum tolerated dose (MTD) for further testing as early imaging changes, presumed to be progression, were common and interfered with the assessment of treatment-related toxicity. The survival outcomes in these and other related studies, although based on small populations, suggest that GSBT may be worthy of further study using clinical and survival endpoints, rather than standard imaging results. The implications for local therapy development are discussed.