Radiotherapy Research Today is a free monthly online journal that collates and summarizes the latest research about Radiotherapy, including details on cancer treatment, side effects.

Radiation dose-volume effects in the brain.

Lawrence YR, Li XA, el Naqa I, Hahn CA, Marks LB, Merchant TE, Dicker AP

Department of Radiation Oncology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA. richard.lawrence@jefferson.edu

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.

Published 22 February 2010 in Int J Radiat Oncol Biol Phys, 76(3): S20-7.
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