The Role of External Beam Radiation Therapy

Brain, Spinal cord, Meninges Primary or Metastatic Metastatic cancers of the CNS are more

common Types of CNS tumours:

Gliomas Spinal cord tumours Intracranial germ cell tumours

Figure 1. The brain and spinal cord of the CNShttp://www.encognitive.com/node/1115

Figure 2. Frequency of all primary CNS gliomas. Adamson, C., et al. (2009) Glioblastoma multiforme: A review of where we have been and where we are going. Expert Opinion on Investigational Drugs, 18(8): 1061-1083

Extensive microvascular infiltration Rapid proliferation High rates of recurrence Presenting features:

Seizures Headaches Focal neurologic deficits

Etiology unknown

Diagnostic workup Patient history and physical examination Magnetic Resonance Imaging (MRI) Contrast-enhanced CT Biopsy – pathologic confirmation

Staged according to the World Health Organisation (WHO) classification system

Table 1. WHO classification system for CNS tumours

Figure 3. Treatment management approach for glioblastoma

External beam vs. Stereotactic, Brachytherapy, Hyperfractionation, Radioenhancers, BCNT, Accelerated, Dose escalation

3DCRT vs. IMRT vs. Rapidarc

Table 2. Recommended techniques for malignant glioma planning and their respective advantages and disadvantages. Wagner, D. et al. (2009) Radiotherapy of malignant gliomas: Comparison of volumetric single arc technique (Rapidarc), dynamic intensity-modulated technique and 3D conformal technique. Radiotherapy and Oncology, 93:593-596

SupineThermoplastic

immobilization mask

CT with intravenous contrast

Figure 4. Contrast enhanced CT of brain. Arrow indicates GBM multiforme. Drislane, F. et al. (2006) Chapter 19: Brain Tumors. Blueprints Neurology, Philadelphia: Lippincott Williams & Wilkins

Post-op MRI scan + CT fusion Target volume: 2-3cm margin around

contrast-enhanced lesion Whole brain radiotherapy

Multifocal gliomas Gliomas crossing midline or involving both

hemispheres

Figure 5. (A) Target delineation of a GBM. GTV outlined in blue. CTV with an additional 2cm margin to cover microscopic disease is represented by the green line. An additional 0.5cm margin is added to create the PTV for daily setup variability. (B) 3 field 3DCRT planned treatment for the same patient. Preusser, M. et al. (2011) Current concepts and management of glioblastoma. Annals of Neurology, 70: 9-21

Recommendations for 2-6 weeks post-surgery

Treatment position same as in simulation Immobilisation mask accuracy within order of

5mm Appropriate QA procedures and treatment

verification carried out 2D-2D matching IGRT can reduce PTV margin to

3mm Dependent on available imaging modalities at

each centre

Patients with GBM have a relatively poor prognosis and much research is needed in the way of improved treatment standards, especially to do with recurrent GBM

Requires MDT approach for treatment Care must be taken in the planning of GBM

Be aware of proximity of OAR, need for partial or whole brain RT and the advantages/disadvantages of different EBRT techniques which may assist in planning

If performing IMRT or Rapidarc, additional QA measure must be taken

Be aware of associated side effects and flag to appropriate member of MDT if thought necessary

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Jones and Bartlett Publishers Greene, F.L. et al. (2002) Chapter 47: Brain and spinal cord. AJCC Cancer Staging Handbook, New York: Springer Hansen, E.K. & Roach III, M. (2010) Part II: Central nervous system. Handbook of Evidence-Based Radiation Oncology, London: Springer Hermanto, U. et al. (2007) Intensity-modulated radiotherapy (IMRT) and conventional three-dimensional conformal radiotherapy for high-grade

gliomas: Does IMRT increase the integral dose to normal brain? International Journal of Radiation Oncology Biology Physics, 67(4): 1135-1144 Kuo, L. et al. (2008) Setup accuracy of a thermoplastic mask system using two-dimensional (2D) on-board imager (OBI) for fractionated stereotactic

radiotherapy (FSRT). Medical Physics, 35(6): 2825 Louis, D.N. et al. (2007) The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathologica, 114: 97-109 Manoj, L. et al. (2011) Review of brain and brain cancer treatment. International Journal of Pharma and Bio Sciences, 2(1): 468-477 Mason, W.P. et al. (2007) Canadian recommendations for the treatment of glioblastoma multiforme. Current Oncology, 14(3): 110-117 Mirimanoff, R.O. et al. (2006) Radiotherapy and temozolomide for newly diagnosed glioblastoma: recursive partitioning analysis of the EORTC

26981/22981-NCIC CE3 phase III randomised trial. Journal of Clinical Oncology, 24: 2563-2569 Mundt, A.J. & Roeske, J. (2011) Chapter 15: Central nervous system tumors: Overview. Image-Guided Radiation Therapy: A Clinical Perspective,

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technique and 3D conformal technique. Radiotherapy and Oncology, 93:593-596