γ-Knife Radiosurgery for Brainstem Lesions: The Wayne State University Experience

Stereotactic radiosurgery (SRS) is increasingly being used for tumors of the brainstem because it suits the anatomical constraints of this area. We now report on the 2-year experience at Wayne State University using γ-knife SRS for such lesions, with an emphasis on toxicity and morbidity. From January 1996 to January 1998, sixteen patients (6 males and 10 females) with lesions in the area of the brainstem were treated with SRS. Average age was 53 years (range 19–80). Nine lesions were malignant; 7 were benign. Median Karnofsky performance status (KPS) prior to SRS was 80 (range 50–100). Median follow-up period from initial diagnosis to analysis, and from the date of SRS to analysis, was 24 months (range 11–73) and 15 months (range 4–29), respectively. Results were analyzed for the whole population treated and then stratified by diagnosis: benign versus malignant. At analysis, 10 (62.6%) patients were alive and 6 (37.5%) were dead. No deaths followed SRS. Values for KPS prior to SRS were compared to 3 months post-SRS. No significant change in KPS scores could be observed for those with benign lesions, but 67% of patients with malignant tumors showed a KPS drop ≥30 points. There was no correlation between the treated volume and survival. At the time of review, no patients had developed new neurological symptoms after SRS. Results for benign lesions indicate that SRS is well tolerated, provides good local control, and does not cause unusual rates of morbidity or mortality. Results for malignant lesions demonstrate that pretreatment performance status influences the post-SRS values. The post-SRS Median Survival (MS) of 10 months for the Malignant Lesions (M) is impressive, in light of the drop of KPS observed; the outcome for such patients is likely determined by the activity of the primary disease process. Our results suggest that SRS in the brainstem is safe, feasible, and merits further study.