Radiation Therapy
A. Gray
= 100 rads (1 centigray = 1 rad)
B. Indications
Tumor; sometimes inoperable AVMs.
C. Doses
Risk of radiation necrosis varies with total dose.
1. Primary tumors: 60 Gy to “involved field” over 6-8 wk (5×/wk).
2. Metastases: 30 Gy to whole brain over 2 wk.
D. SEs
1. Acute: N/V, worsened deficits. Seizures rare; usually from edema. Increase steroids.
2. Subacute (weeks to months): Lethargy from brain XRT, Lhermitte’s sign from spine radiation therapy.
3. Late (months to years):
a. Sx: Dementia, focal deficits, endocrine changes.
b. Causes: Radiation necrosis, leukoencephalopathy, pituitary insufficiency, new tumors (gliomas, GBM, meningiomas, nerve sheath tumors), radiation myelopathy (usually from cervical > thoracic radiation therapy).
c. Tests: PET, SPECT, or MRS to tell recurrent tumor from radiation necrosis. May need biopsy.
d. RxRelated posts:
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