Brain OAR constraint
Limit hotspots >60Gy
Brainstem OAR constraint
Max dose <54Gy
Brainstem PRV max dose <60Gy (PRV includes a margin which is added around the organ at risk to compensate for that organ’s geometric uncertainties)
Cochlea OAR constraintq=
Mean dose <45Gy
<5% receives 55Gy
Globe (incl. retina) oar constraint
Mean dose <35Gy
Max dose <50Gy
Retina oar constraint
ideal <45Gy
Acceptable <50Gy
Hippocampus OAR constraint
ALARA
Mean <5-10Gy
Where possible spare the hippocampus contralateral to the tumour
Inner ear OAR constraint
Aim to keep doses<40Gy
max <45Gy
Lens OAR constraint
ideal max dose <10Gy
Optic chasm OAR
max dose <54Gy
risk of radiation induced optic neuropathy <3-7% at dose 55-60Gy
risk of RION increases to 7-20% for doses >60Gy in conventional fractionation
Optic chiasm OAR
max dose <54Gy
Pituitary gland OAR
mean <45Gy include pituitary stalk in contouring
Spinal cord OAR
max dose <45Gy
Max dose:
<50 Gy, to keep risk of myelopathy ≤0.2%
<60 Gy, to keep risk of myelopathy ≤6%
<69 Gy, to keep risk of myelopathy ≤50%
Acute and late side effects from treatment for GBM (radiation only)
Acute:
- fatigue
- alopecia
- Skin reaction
- headaches
- nausea and vomiting
- seizure
- worsening of pre-existing neurological symptoms
Subacute
- somnolence syndrome
- brain oedema requiring long term steroid use and associated toxicities
Late:
- Alopecia
- Cognitive changes
- neurovascular changes
- neuroendocrine abnormalities (may result in growth hormone, adenocorticotrophic hormone (ACTH) and thyroid-stimulating hormone (TSH) deficiencies)
- cataract formation
- blindness due to RION
- hearing loss/ototoxicity
- Necrosis
- second malignancy
