Radiosurgical decompression for benign perioptic tumors causing compressive cranial neuropathies: a feasible alternative to microsurgery?

Abstract

Several studies have reported the efficacy and safety of hypofractionated stereotactic radiosurgery (hSRS) in the treatment of benign perioptic tumors. This study went further and evaluated the feasibility of hSRS in the treatment of those causing compressive cranial neuropathies (CCNs) among perioptic tumors with special consideration of functional improvement. Twenty-six patients with CCNs (CN II = 19; CN III/IV/VI = 9; CN V = 3) caused by perioptic tumors underwent hSRS between 2011 and 2015. hSRS was delivered in five fractions with a median marginal dose of 27.8 Gy (≈14 Gy in a single fraction, assuming an α/β of three) to a tumor volume of 8.2 ± 8.3 cm. All tumors except one shrank after treatment, with a mean volume decrease of 35 % (range 4-84 %) during the mean follow-up period of 20 months. In 19 patients (38 eyes) with compressive optic neuropathy, vision improved in 55.3 % of eyes (n = 21), was unchanged in 36.8 % (n = 14), and worsened in 7.9 % (n = 3) (2.6 % after excluding two eyes deteriorated due to transient tumor swelling). A higher conformity index (p = 0.034) and volume of the optic apparatus receiving >23.0 Gy (p = 0.019) were associated with greater tumor shrinkage. A greater decrease in tumor volume (p = 0.035) was associated with a better improvement in vision. Ophthalmoplegia and facial hypesthesia improved in six of nine (66.7 %) and three of three (100 %) patients, respectively. There was no newly developed neurological deficit. Decompressive SRS for benign perioptic tumors causing CCN is feasible using hypofractionation, representing a useful alternative to microsurgical resection.

Clinical outcomes of fractionated stereotactic radiosurgery in treating perioptic meningiomas and schwannomas: A single-institutional experience

“…In assessing tumor control, a greater than 20% increase or decrease in tumor volume post-FSRS compared to pre-FSRS was considered an ''Increase" or ''Decrease", respectively. Tumor volume changes less than 20% was considered ''Stationary" [3,9,17]. The ''decreased" and ''stationary" groups were considered a favorable outcome of tumor control.…”

Dosimetric Parameters Associated with the Long-Term Oncologic Outcomes of Gamma Knife Surgery for Sellar and Parasellar Tumors in Pediatric Patients

“…There may still be a dose gradient between the D 98% value for long-term tumor control and the tolerable maximum point dose to the optic apparatus. The tumors apart > 2 mm from the optic apparatus usually meet the required dose gradient due to the steep dose fall-off of GKS at the margin of the target; otherwise, fractionated radiosurgery may help lower the dose gradient [7]. These results are based on data derived from heterogeneous tumors with different biological behaviors, as well as a small sample size for each tumor type.…”

“…A steep radiation dose fall-off at the margin of the target in SRS spares the surrounding neural tissues from the harmful effect of radiation [6]. Recent advances in SRS hypofractionation systems have reduced the risk of radiation-induced optic neuropathy (RION), contributing to the expansion of SRS application to tumors in these regions [7]. However, the long-term e cacy and safety of SRS for sellar and parasellar tumors in children have not been clearly elucidated.…”