Treatment for Glioblastoma Multiforme: Current Guidelines and Canadian Practice

Purpose: Our survey aimed to document variability in the practice patterns of Canadian radiation oncologists treating high-grade brain tumours. Materials and Methods: A 20-question survey was developed to address various aspects of treatment: (1) Guidelines used; (2) Types of fusion protocols used; (3) Number of treatment phases; (4) Margins for volume delineation; (5) Dose constraints. The survey was sent to Canadian radiation oncologists currently treating the central nervous system (CNS) as one of their primary sites. Results: We attained a 56% response rate from radiation oncologists across Canada treating CNS sites. In their practice, 14% of respondents reported following guidelines from the European Organisation for Research and Treatment of Cancer; 32%, from the Radiation Therapy Oncology Group; and 56%, centre-specific guidelines. Single-phase treatment was reported by 60% of clinicians, and two-phase or multi-phase treatments, by 37%. For clinicians treating in single phase, margins from the gross treatment volume (GTV) to the planning treatment volume (PTV) included 0.5 cm (6%), 1 cm (6%), 1.5 cm (25%), 2.0 cm (56%), 2.5 cm (25%), and 3 cm (12.5%), with some respondents selecting more than one standard margin. For clinicians treating in multiple phases, margins from gtv to ptv in phase 2 included 1 cm (10%), 2.0 cm (40%), 2.5 cm (30%), and 3.0 cm (20%). Variability was also observed in dose constraints to critical structures. All respondents trimmed their margins to bony structures.