CNS Tumours

Question 1

Discuss the investigations used to diagnose CNS tumours

Answer 1

• Clinical examination/patient history
• Plain X-ray [calcification, erosion of sella turcica]
• CT w/ contrast
• MRI
• Cerebral angiography [circulation, exclude AVM]
• Biopsy [malignant or benign]

Question 2

What staging system is used for CNS tumours?

Answer 2

WHO grading system
1. least malignant; slow growing
2. Slow growing
3. Malignant
4. Most Malignant

Question 3

Describe the common routes of spread for CNS tumours

Answer 3

• Through white matter .i.e corpus callosum to other hemisphere
• Along surface of meninges [menigioma]
• Via CSF to meninges and spinal cord

Question 4

What treatment management options are considered for CNS tumours?

Answer 4

• Neurosurgery
• RT
• Steriods & Chemo
• Supportive Care [symptoms]
• Clinical Trials

Question 5

What advantages are there of taking a biopsy of a CNS tumour?

Answer 5

• Can relieve pressure effects of tumour
• Allows steriod doses to be reduced
• Facilitates RT

Question 6

What chemotherapy techniques have been developed to circumvent the blood-brain barrier?

Answer 6

• Wafers - placed in area tumour removed from
• Intrathecal chemo [CSF via lumbar puncture]
• IV & Oral Chemo [some Grade 3 Gliomas]

Question 7

What is the primary role of steriods in the treatment management of CNS tumours?

Answer 7

To treat odema in the brain

Question 8

What is the name of the primary steroid used for CNS tumours?

Answer 8

Dexamethosone

Question 9

What are the main side effects associated with using steriods to manage odema?

Answer 9

• Weight gain
• Muscle weakness
• Gastric irritation
• Diabetes

Question 10

What steps should be taken when prescribing steriods for managing oedmea in the brain?

Answer 10

• Should be managed with minimum dose possible
• Reduce dose gradually - do not stop abruptly
• Patient should carry a steriod card

Question 11

What are the OAR tolerance doses for RT of CNS tumours?

Answer 11

• Brain: 54-60 Gy 30#
• Brainstem: 54 Gy 30#
• Optic nerves: 45Gy 25#
• Pituitary & hypothal: 20-24Gy
• Lacrimal gland: 20Gy
• Lens: 5-6Gy over 30# gives cataracts
• Middle & Inner Ear: 60Gy
• Alopecia: permanent 50% patients 45Gy 30#
• Spinal Cord: 50Gy 30#

Question 12

Discuss the planning considerations for RT for CNS tumours?

Answer 12

• Minimise vol of brain outwith PTV recieving 40Gy+
• Mean dose to brain outwith PTV < 24GY
• VMAT standard technique
• Often non-coplanar fields used (floor rotations)

Question 13

What are the common acute side effects of RT on CNS tumuours?

Answer 13

• Hair loss
• Erythema
• Somnolence
• Hearing loss
• Raised intracranial pressure
• Headache
• Dysphasia (speech impairment)
• Nausea
• Blurred vision
• Unsteady gait

Question 14

What are the possible late side effects of RT for CNS tumours?

Answer 14

• Necrosis
• Fibrosis
• Cognitive decline
• Neuro-endocrine abnormalities
• Demyelination (nerve damage)
• Vascular damage