Linear accelerator-based stereotactic radiosurgery for acoustic schwannomas

Area of Science:

• Neurosurgery
• Radiation Oncology
• Oncology

Background:

• Stereotactic radiosurgery (SRS) is an emerging treatment for acoustic schwannomas, particularly for patients unsuitable for surgery.
• Existing data predominantly features gamma knife treatments, necessitating research into alternative SRS modalities.
• Linear accelerator (LINAC)-based SRS offers a viable alternative for acoustic schwannoma management.

Purpose of the Study:

• To evaluate the efficacy and safety of linear accelerator-based stereotactic radiosurgery (SRS) for treating acoustic schwannomas.
• To present the largest series of acoustic schwannoma patients treated with LINAC-based SRS.
• To compare LINAC-based SRS outcomes with existing gamma knife data.

Main Methods:

• A cohort of 32 patients with acoustic schwannomas underwent LINAC-based SRS between 1988 and 1993.
• Treatment involved peripheral doses ranging from 10-22.5 Gy (mean 15.5 Gy) at 68-90% isodose lines.
• Tumor sizes treated were larger than typically reported in gamma knife series, with collimator sizes ranging from 12-35 mm.

Main Results:

• At 1, 2, and 3 years post-treatment, tumor regression rates were 63%, 73%, and 78%, respectively.
• No instances of tumor progression were observed after SRS.
• Complications occurred in 22% of patients, including new cranial nerve deficits (5th/7th), ataxia, and hydrocephalus.

Conclusions:

• LINAC-based SRS demonstrates excellent short-term local control for acoustic schwannomas.
• The complication rate associated with LINAC-based SRS is relatively low.
• Outcomes appear favorable when compared to gamma knife-based SRS, warranting further long-term evaluation.