Radiosurgery for primary malignant brain tumors.

Despite the ability of surgery, radiotherapy, and chemotherapy to prolong survival in patients with glioblastoma multiforme (GBM), most patients succumb to their disease, usually as a result of local tumor persistence or recurrence. Stereotactic radiosurgery (SRS) allows a substantial increase in total dose at sites of greatest tumor cell density while sparing most of the normal brain, resulting in significantly improved survival. SRS was designed as a technique to deliver a large single dose of radiation to a small and focal target: two of its hallmarks are the focal distribution of dose and the inverse relationship between dose and volume. Acute complications of SRS are related to edema and are manifested as a worsening of pre-existing symptoms: seizure, aphasia, and motor deficits--these are treatable with steroids and are transient in the majority of cases. The actuarial risk of undergoing reoperation was 33% at 12 months and 48% at 24 months, following SRS. Patterns of failure were similar following brachytherapy or SRS as treatment for recurrent GBM with most patients experiencing marginal failure outside the original treatment volume. Patients with small (< 30 mm diameter), radiographically distinct and focally recurrent GBM should be considered for SRS. Larger lesions (> 30 mm diameter), especially those adjacent to eloquent cortex or critical white matter pathways, must be evaluated with caution. The potential for acute toxicity associated with SRS increases substantially for larger lesions. There is a significant survival advantage using SRS in many patients with gliomas, especially if appropriately used with surgery and other adjuvant therapy.