After surgery, radiation therapy is the most important treatment for intracranial tumors and can often be supplemented with surgical treatment. Radiation therapy is often administered in the post-operative phase.
In cases where surgical treatment is impossible due to the location of the tumor, and where surgery is associated with an unacceptably high risk of a mutilating neurological outcome, radiation can replace surgery. This applies especially to the use of stereotactic radiation techniques on small tumors (< 3 cm in diameter) with limited surrounding infiltration.
Radiated tissue volume, the number of fractions, fraction dose and total dose must be adapted to the individual patient on the basis of age, tumor type, intracranial tumor localization and the normal tissue's tolerance for radiation.
Generally, total doses of up to 50–60 Gy, given with in a fractional dose of 1.8—2 Gy over a treatment period of 5-6 weeks will be tolerated in adult patients.
For malignant, infiltrating tumors (gliomas grade III–IV), the addition of local radiation therapy can destroy infiltrating cancer cells around the main tumor and thereby improve survival.
For medulloblastoma or germinoma, where the risk of spinal fluid borne metastasis within the central nerve system is high, radiation therapy targeted at the entire central nervous system (possibly limited to the ventricular system with germinomas) is necessary in order to avoid microscopic tumor spreading.
For brain metastases, the entire brain is often radiated, but stereotactic treatment is an alternative for max. 3 metastases with a metastasis diameter of < 3 cm.
Post-operative radiation treatment is routine for glioblastoma and anaplastic gliomas. For these conditions, radiation does extend life but is not curative. Radiation can reduce symptoms for low-grade gliomas, but is probably not life-extending. Indications for radiation therapy for low-grade gliomas must therefore be evaluated individually.
Radiation therapy can regularly arrest the growth of locally aggressive, inoperable pituitary gland adenomas and meningiomas. These tumors will usually persist after external radiation therapy, but this is rarely of clinical significance, provided that further tumor growth is stopped.
For medulloblastoma, germinomas and lymphomas, radiation is part of the curative treatment plan and may be sufficient to cure some patients.