Cranial irradiation is used to treat patients with primary or metastatic brain tumors and as prophylaxis for selected patients at high risk of neoplastic involvement of the nervous system. A full understanding of the potential consequences associated with cranial irradiation is needed both to manage potential complications and to properly counsel patients and/or families prior to treatment.
The primary factors influencing the likelihood of developing complications include the volume of normal brain tissue treated, the total radiation dose, and the fractionation schedule. The likelihood of brain toxicity also increases in the young (ie, <5 years old) and the elderly and with use of concurrent or sequential chemotherapy. Poor characterized genetic factors also may make certain individuals more susceptible to otherwise safe doses of radiation.
The complications of radiation therapy (RT) are usually divided into acute effects that can occur during the course of radiation, early-delayed effects that appear two to four months after radiation, and late effects that can develop more than 90 days after the initiation of RT. The Radiation Therapy Oncology Group (RTOG) has established specific grading criteria for acute and delayed toxicities (table 1 and table 2) .The distinction between early and late complications is also important since acute and early-delayed complications are usually reversible while late reactions often are not.
The acute complications of both standard fractionated cranial irradiation and stereotactic radiosurgery will be reviewed here. The late complications of cranial irradiation and complications of spinal cord and peripheral nerve are discussed elsewhere. (See "Delayed complications of cranial irradiation" and "Complications of spinal cord irradiation" and "Complications of peripheral nerve irradiation".)
STANDARD FRACTIONATED RADIATION
Acute side effects occurring during standard fractionated brain radiation using contemporary techniques are typically mild and manageable with basic supportive care. Some of the more common and uncommon toxicities are discussed below.