Introduction: To evaluate preliminary outcomes for a cohort of patients who were treated with multisession Gamma Knife radiosurgery (GKRS) using the new noninvasive vacuum-assisted immobilization system.
Methods: A retrospective review was performed of 15 consecutive cases treated with multisession GKRS. Radiosurgical targets included 12 meningiomas, 1 nonfunctioning pituitary adenoma, 1 growth hormoneesecreting pituitary ad- enoma, and 1 pilocytic astrocytoma. GKRS was delivered in 3e5 sessions to a mean tumor volume of 8.55 mL (median, 7.3 mL; range, 1.24e22.7 mL) with a mean margin dose of 19.7 Gy (median, 20 Gy; range, 15e25 Gy). The optic nerves, chiasm, and tracts received mean doses of 3.5 Gy (range, 0.7e5.7 Gy), 3.1 Gy (range, 1e4.4 Gy), and 2.6 Gy (range, 0.83e5.45 Gy) per session. Mean biologic equivalent dose (a/b [ 2.5) was 60.9 Gy (median, 60 Gy; range, 45e79.8 Gy). Follow-up examinations were performed at 3- to 6-month intervals.
Results: Mean follow-up was 17.7 months (median, 13.8 months; range, 4e44.3 months), and tumor control was noted in all patients, with regression in 5 patients and stability in 10 patients. New neurologic deficits developed in 3 patients after treatment, but none of these deficits were permanent. Resection was performed in 1 patient with expressive aphasia with worsening of peritu- moral T2 signal but a stable tumor on follow-up magnetic resonance imaging. The other 2 patients were managed conservatively for minor complications (ptosis, taste dysfunction), and their symptoms resolved. No patients developed deterioration in vision during the follow-up period.
Conclusions: - CONCLUSIONS: Preliminary experience with multisession GKRS appears promising, with reasonable tumor control and complication rates. Multisession stereotactic radiosurgery may expand the treatment envelope for intracranial pathologies, including targets with larger volumes and locations in close proximity to radiosensitive structures.
Patient Care: Gamma Knife radiosurgery performed with the new Extend system facilitates multisession radio- surgery in a truly noninvasive fashion. Preliminary data from 15 patients treated demonstrate promising results. Multisession stereotactic radiosurgery may lead to more routine treatment of lesions in close proximity to radiosensitive or eloquent structures, large-volume lesions, and lesions that may require repeated treatments.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Describe the indications for multisession Gamma Knife radiosurgery using a non-invasive relocatable frame.
2) Describe the preliminary results of the new Gamma Knife radiosurgery performed with the new Extend system
3) Describe the difference between the new Gamma Knife Extend system and the current stereotactic frame using pins.