Stereotactic radiosurgery and hypofractionated stereotactic radiotherapy for management of vestibular schwannomas: initial experience with 17 cases.

BACKGROUND: Nowadays radiation treatment of patients with vestibular schwannomas (VSs) applied either as stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) represents a real alternative to surgical tumor resection. METHODS: During 2010-2011, 17 consecutive patients (19-75 years old) with a VS underwent treatment with SRS or SRT in our center. Microsurgery was initially offered in all cases but was declined for various reasons. Five lesions recurred after the initial partial resection. Two other patients with neurofibromatosis type 2 underwent initial surgery for a large tumor on the contralateral side and had the only hearing ear on the side of the remaining neoplasm. Three elderly persons had somatic problems that were too severe for them to undergo craniotomy. Five small tumors without brain stem compression underwent single-fraction SRS (12.0-12.5 Gy at the 80 % isodose line). Other patients, mainly with large neoplasms that caused brain stem compression, were treated with hypofractionated SRT (five or six daily fractions at a dose of 4.5-5.0 Gy each). Treatment was performed with a dedicated linear accelerator (Elekta Axesse). Various stereotactic fixation devices were used: Leksell G frame, noninvasive HeadFIX frame, reinforced thermoplastic masks. RESULTS: No adverse reactions or complications were seen in any case. Within 3 months after treatment three tumors demonstrated shrinkage accompanied by improvement of the neurological functions. CONCLUSION: Radiation treatment, particularly hypofractionated SRT, can be safely applied even for large VSs that cause brain stem compression and are accompanied by prominent neurological symptoms.

Benchmarking Tests of Contemporary SRS Platforms: Have Technological Developments Resulted in Improved Treatment Plan Quality?

PURPOSE: Stereotactic radiosurgery treatment delivery can be performed with a range of devices, each of which have evolved over recent years. We sought to evaluate the differences in performance of contemporary stereotactic radiosurgery platforms and also to compare them with earlier platform iterations from a previous benchmarking study. METHODS AND MATERIALS: The following platforms were selected as "state of the art" in 2022: Gamma Knife Icon (GK), CyberKnife S7 (CK), Brainlab Elements (Elekta VersaHD and Varian TrueBeam), Varian Edge with HyperArc (HA), and Zap-X. Six benchmarking cases were used from a 2016 study. To reflect the evolution of increasing numbers of metastases treated per patient, a 14-target case was added. The 28 targets among the 7 patients ranged from 0.02 to 7.2 cc in volume. Participating centers were sent images and contours for each patient and asked to plan them to the best of their ability. Although some variation in local practice was allowed (eg, margins), groups were asked to prescribe a specified dose to each target and tolerance doses to organs at risk were agreed upon. Parameters compared included coverage, selectivity, Paddick conformity index, gradient index (GI), R50%, efficiency index, doses to organs at risk, and planning and treatment times. RESULTS: Mean coverage for all targets ranged from 98.2% (Brainlab/Elekta) to 99.7% (HA-6X). Paddick conformity index values ranged from 0.722 (Zap-X) to 0.894 (CK). GI ranged from a mean of 3.52 (GK), representing the steepest dose gradient, to 5.08 (HA-10X). The GI appeared to follow a trend with beam energy, with the lowest values from the lower energy platforms (GK, 1.25 MeV; Zap-X, 3 MV) and the highest value from the highest energy (HA-10X). Mean R50% values ranged from 4.48 (GK) to 5.98 (HA-10X). Treatment times were lowest for C-arm linear accelerators. CONCLUSIONS: Compared with earlier studies, newer equipment appears to deliver higher quality treatments. CyberKnife and linear accelerator platforms appear to give higher conformity whereas lower energy platforms yield a steeper dose gradient.