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Side Effects of Radiation Therapy (RT)



General Side Effects


Side Effects from RT can be classified into three groups:

1. EARLY (during treatment and the first month after RT)

2. EARLY DELAYED (up to 6 months after RT)

  • Scattered astrocytic and microglial reactions, perivascular collections of mononuclear cells and demyelination seen.

3. LATE (90 days to many years after RT)

  • Late effects in the brain include the break down of neural tissue with myelin destruction, proliferative and degenerative changes in glial cells. 
  • Vascular changes occur with endothelial cell loss, proliferation, capillary occlusion, degeneration and hemorrhagic exudates. 
  • Eventually this leads to vasogenic edema and cerebral atrophy.


Late Effects can be classified according to their severity.

The classification scheme outlined by the RTOG (Radiation Therapy Oncology Group) labels neurological symptoms into one of four categories based on their severity. 


The classification system is as follows:

Symptom Grade Description


No change above baseline


Fully functional status
Minor neurologic findings, no medications needed


Neurologic findings sufficient to require home care
Medications are required for symptoms eg. Steroids, Anti-seizure medications


Neurologic findings require hospitalization for initial management


Serious neurologic impairment despite medication

- paralysis
- coma
- seizures (>3 times/week)

Hospitalization required



(Taken from Radiation Therapy Oncology Group website)





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