Central Nervous System
Radionecrosis
Radionecrosis or radiation necrosis refers to damage or death of brain tissue (focal) as a result of radiation therapy (RT). Radiation necrosis is progressive and often fatal.
Epidemiology:
- Radiation necrosis is estimated to occur in 5% or less of patients
- This problem may occur at any time between 3 - 6 months to more than 10 years following high dose cranial RT.
- The peak time of presentation is within 2 years post-treatment with necrosis becoming apparent up to 3 years.
Risk factors:
- High dose RT
- Increased fraction size of RT
- Subsequent treatment with chemotherapy
Signs and symptoms:
Clinical picture is usually progressive and irreversible.
- Memory loss
- Dementia
- Confusion
- Depression
- Agitation
- Personality changes
- Symptoms mimicking recurrent tumor with increased intracranial pressure:
- Vomiting
- Headache
- Diplopia
- Papilledema
- Focal motor signs
Radiology
- Radiation necrosis causes a mass lesion on MRI and CT with surrounding edema.
- Diffuse necrosis is described as a “Swiss cheese” pattern
- Central necrosis is described as a “soap bubble” pattern
- Differentiation from tumor recurrence is often difficult.
- In order to distinguish between necrosis and recurrence you can use:
- Diffusion-weighted MRI
- PET scan
(positive and negative predictive values for
tumor of 80-90%)
- Radiation necrosis does not show increased uptake of FDG
- Recurrence shows increased uptake of FDG.
Pathology
- Pathology shows vascular changes with loss of myelination due to oligdendrocytic death
- However, establishing the diagnosis by biopsy is usually dangerous and surgery is only indicated if tumor recurrence or progression is strongly suspected
Treatment
- Dexamethasone
- Surgical debulking or removal if possible may be the only effective therapy in cases associated with significant mass effect
- Hyperbaric oxygen (used with variable success)
- Anticoagulation
- Bevacizumab: This drug prevents blood vessel growth in tumors by blocking vascular endothelial growth factor (VEGF). There are reports that this drug can be beneficial in the treatment of radiation necrosis by decreasing capillary leakage and associated brain edema.
