Contouring Guidelines for Glioma

Introduction to Glioma Contouring

The clinical target volume (CTV) for gliomas should include a safety margin of 20 mm outside the gross tumor volume (GTV) in all three dimensions, which can be reduced depending on the grade, histological type, and tumor volume, as recommended by the British Journal of Cancer 1

MRI should be used in preference to CT scanning as the standard diagnostic tool for glioma contouring, with images taken using the same technique in three dimensions, according to the British Journal of Cancer 1
T1-weighted (with and without contrast medium), T2-weighted MR images and/or fluid-attenuated inversion recovery (FLAIR) imaging should be undertaken as standard, as per the British Journal of Cancer 1
MR images should be converted into a digital format on a numerical support system (e.g., CD) for possible subsequent dosimetric studies, as recommended by the British Journal of Cancer 1
Functional MRI, MR diffusion imaging, MR perfusion studies, and/or proton MR spectroscopy can be combined with standard imaging as options, according to the British Journal of Cancer 1
PET or SPECT scans can be performed in clinical trial settings, as per the British Journal of Cancer 1

For glioblastoma (WHO grade IV): GTV includes the surgical bed plus residual tumor area identified on T1-weighted MRI with contrast enhancement, as recommended by the National Comprehensive Cancer Network 2

The safety margin can be reduced depending on the grade, histological type, and tumor volume, as recommended by the British Journal of Cancer 1

Non-coplanar focalized multiple beam (3-5) should be used to minimize the total fractionated dose delivered to the non-diseased brain, according to the British Journal of Cancer 1
Dose-volume histograms can be useful for defining the best treatment plan, as per the British Journal of Cancer 1

All fields should be irradiated the same day with a fractionated dose varying from 1.8 to 2 Gy per fraction per day, five times per week, as recommended by the British Journal of Cancer 1
The dose should be adapted according to the histological type and grade of the lesion and should not exceed a total of 60 Gy, according to the British Journal of Cancer 1

Prophylactic corticosteroid treatment should not be prescribed routinely but can be used to reduce the risk of acute or early-delayed encephalopathy (radiation-induced edema), as recommended by the British Journal of Cancer 1
Clinical and/or radiological deterioration in the 2 months after the end of radiotherapy should be interpreted with caution and not automatically considered as treatment failure, according to the British Journal of Cancer 1
Patients over 50 years old and/or with previous vascular disease (hypertension, diabetes, hyperlipidemia) have an increased risk for late neurological complications (radionecrosis, radiation-induced leukoencephalopathy), as per the British Journal of Cancer 1

Molecular characterization should complement standard histologic assessment to provide additional diagnostic and prognostic information that may aid in treatment selection, as recommended by the National Comprehensive Cancer Network 3
MGMT promoter methylation, IDH mutations, and co-deletions of 1p/19q should be determined depending on the histological and clinical context, according to the European Society for Medical Oncology 4
Molecular markers can help identify tumor subtypes that may benefit from specific treatment approaches, as recommended by the National Comprehensive Cancer Network and the European Society for Medical Oncology 3, 5