Radiation dose-volume effects in the brain.
We have reviewed the published data regarding radiotherapy (RT)-induced brain injury. Radiation necrosis appears a median of 1-2 years after RT; however, cognitive decline develops over many years. The incidence and severity is dose and volume dependent and can also be increased by chemotherapy, age, diabetes, and spatial factors. For fractionated RT with a fraction size of <2.5 Gy, an incidence of radiation necrosis of 5% and 10% is predicted to occur at a biologically effective dose of 120 Gy (range, 100-140) and 150 Gy (range, 140-170), respectively. For twice-daily fractionation, a steep increase in toxicity appears to occur when the biologically effective dose is >80 Gy. For large fraction sizes (>or=2.5 Gy), the incidence and severity of toxicity is unpredictable. For single fraction radiosurgery, a clear correlation has been demonstrated between the target size and the risk of adverse events. Substantial variation among different centers' reported outcomes have prevented us from making toxicity-risk predictions. Cognitive dysfunction in children is largely seen for whole brain doses of >or=18 Gy. No substantial evidence has shown that RT induces irreversible cognitive decline in adults within 4 years of RT.
Lawrence
Yaacov Richard
YR
Department of Radiation Oncology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA. richard.lawrence@jefferson.edu
Li
X Allen
XA
el Naqa
Issam
I
Hahn
Carol A
CA
Marks
Lawrence B
LB
Merchant
Thomas E
TE
Dicker
Adam P
AP
D000328:Adult; D000367:Age Factors; D001921:Brain / Q000473:pathology / Q000528:radiation effects*; D003072:Cognition Disorders / Q000209:etiology*; D016371:Cranial Irradiation / Q000009:adverse effects / Q000379:methods; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008954:Models, Biological; D008962:Models, Theoretical; D009336:Necrosis / Q000209:etiology; D011836:Radiation Tolerance; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods