Single-Fraction Stereotactic Radiosurgery for Benign Perioptic Meningiomas: A Strategy for Long-Term Tumor Control...

Lower doses of single-fraction stereotactic radiosurgery (SF-SRS) are typically prescribed for perioptic meningiomas (POMs) due to concerns about radiation-induced optic neuropathy (RION). However, comprehensive long-term follow-up data on both tumor control and RION occurrence are currently lacking. This study endeavored to formulate safe and practical strategies for the implementation of SF-SRS in POMs, utilizing extensive ten-year follow-up data.

We retrospectively analyzed patients who underwent SF-SRS for POMs (< 2 mm from the optic apparatus [OA]) and who were followed up for more than ten years at our institution. Correlations between diverse dosimetric factors irradiated to the tumor and the OA and their respective impacts on tumor control and RION were examined.

Thirty patients were included (a median follow-up: 152 months). A dose of 12.7 ± 3.1 Gy was delivered to the gross tumor volume of 4.8 ± 5.1 cm³ with a coverage rate of 76.7 ± 19.1%, yielding a D_98% of 7.0 ± 4.7 Gy. The actuarial 5- and 10-year progression-free survival rates were 90% and 70%, respectively (overall tumor control in 57%). Treatment failure occurred in a delayed fashion at 107 ± 55 (20-200) months after stereotactic radiosurgery (SRS). Coverage was associated with long-term tumor control (P = 0.004, cutoff value: 81%). Among patients who retained valid vision, the maximum dose to the OA was 7.2 ± 1.6 Gy (4.8-12.9) Gy, and visual decline attributed to tumor progression manifested in two patients at 116 months and 103 months post-SRS, with no occurrence of RION.

Inadequate tumor coverage near the OA during SF-SRS for POMs, driven by concerns about RION, resulted in a significant incidence of long-term tumor progression and subsequent visual deterioration. Clarifying the optimal dose range is crucial for achieving sustained tumor control and preventing RION following SF-SRS.