CNS

Question 1

CNS Tumour types

Answer 1

PNET - Primitive neuroectodermal tumours
Pinealoblastoma - rare
Medullablastoma - most common childhood brain tumour

Question 2

Characteristics of CNS tumours

Answer 2

Highly invasive
Spread rapidly through CSF
60% survival after 5 years
20% have spread to SC before diagnosis

Question 3

Epidemiology - medullablastoma

Answer 3

20% of childhood brain tumours, more common in males than female

Question 4

Medullablastoma signs and symptoms

Answer 4

Headache
Vomiting
Irritability
Problems with motor function

Question 5

Glioblastoma signs and symptoms

Answer 5

Headaches
Seizures
Vomiting
Trouble speaking
Blurred vision

Question 6

Clinical management of CNS tumours

Answer 6

Dependent of risk/staging
Surgery
Craniospinal irradiation
Adjuvant chemo

Question 7

Fields

Answer 7

Usually 2-3 fields
Dependent on patient size
2 lateral for brain
1-2 post fields for spine

Question 8

Junction considerations

Answer 8

The junction for lateral fields and posterior spine field should abut
To ensure this, collimator of lateral field is changed until the junction abutts

Question 9

Overshoot

Answer 9

Ensure overshoot ant, sup and post
However, inferiorly, 0 jaw can be used by placing iso close to eyes

Question 10

Spinal field boundaries

Answer 10

From C-spine to 2nd/4th Sacral foraminifera to include sacral nerve roots
Depending on spine length 1 or 2 isocentres may be requires

Question 11

Spinal beams

Answer 11

2 fields adjoining to cover sup-inf
An anterior arc (1/4 arc) may also be required
Posterior fields are only 3/4 arcs

Question 12

Brain/skull CNS VMAT technique

Answer 12

Usually 1-2 arcs
An extra arc using floor turn (non-coplanar) to achieve OAR tolerances

Question 13

Patient positioning considerations

Answer 13

Chin position is crucial
Too tucked in (junction edge)/too extended (causes neck rolls)

Question 14

Moving junction

Answer 14

Junction between the spinal fields are moved every 4-5 fractions to reduce hot/cold spots and create homogeneity
Can be moved 1cm inf or sup

Question 15

ISOCENTRE

Answer 15

2-3 ISO
Ant-post and laterally in line

Question 16

Junctions and gaps

Answer 16

Gaps are created between the two abutting junctions of spinal fields
The fields intersect in spinal cord

Question 17

Advantages of prone positioning

Answer 17

Access to spine - palpation for setup
Skin marks for junctions
General accuracy

Question 18

Advantages of supine

Answer 18

Development of new technologies
Paeds consideration - access to GA, feeling comfortable and secure

Question 19

Prone positioning setup

Answer 19

Torso & legs elevated and supported
Styrofoam Board; and/or Vac Bag; other?
Cushion or bolster under ankles
Head supported with a comfortable face-rest
Prone pillow; mask; two-piece shell?
Arms by sides with shoulders supported and drawn inf
Minimise obscuring vertebrae on lateral films
C-Spine drawn horizontal
Ensure no skin folds on back of the neck
Posterior surface as level as possible with rest of back
Chin not tucked too far
Post spine field should not diverge into the mouth.

Question 20

Supine positioning setup

Answer 20

Supine, straight and level
Ideally a Vac Bag for support and reproducibility
If no Vac-Bag, bolster under knees, +/- footstocks
Head and shoulders in mask
For reproducibility and field placement marks
Arms by sides with shoulders supported and drawn inf
Minimise obscuring vertebrae on lateral films
C-Spine as horizontal as possible
Try to maintain neck as level as possible with rest of back
Chin raised only to avoid exit from post spine field
Post spine field should not diverge into the mouth.

Question 21

treatment side effects

Answer 21

Erythema, dry and moist desquamation and
oedema
Hair loss
20GY to 40Gy: Temporary hair loss
> 40Gy: Hair loss may be permanent
Drowsiness & lethargy
Decreased mental status/ cognitive impairment
Worsening of tumour symptoms

Cognitive impairment can include:
Decreased IQ
Decreased visual, spatial, motor, fine motor,
memory, and arithmetic skills
Increases in children < 7 yo

Question 22

Patient Care

Answer 22

Assess patient well being: esp. emotional stability
Paediatrics
May need more time/ be patient
Prepare a separate area to talk
Patients can be aggressive
Must consider parent’s needs as well
Encourage patients to eat well and rest
Weekly blood tests