Fractionated Stereotactic Radiotherapy vs. Stereotactic Radiosurgery for Vestibular Schwannoma: Local Control, Hearing Preservation, and Toxicities

Abstract

The use of radiation therapy (RT) in vestibular schwannoma (VS) is well-established, but limited studies detail outcomes in patients treated with fractionated stereotactic radiotherapy (FSRT) versus stereotactic radiosurgery (SRS). In this study, we provide an outcome-based comparison of FSRT versus SRS in patients with VS with emphases on local control, hearing preservation, and toxicities. We hypothesize that FSRT and SRS will have similar rates of local control with FSRT having improved rates of hearing preservation. Patients treated at a single tertiary referral center between 2013 and 2018 for VS using FSRT (46.8 Gy in 26 fractions) or SRS (12 Gy in 1 fraction) were identified. Records from radiation oncology, neurosurgery, and otolaryngology were included. Endpoints included local control, defined as absence of tumor progression or need for salvage treatment, hearing preservation, quantified by Gardner-Robinson (GR) scoring and defined as maintaining GR1-2 hearing, and toxicities as per Common Terminology Criteria for Adverse Events (CTCAE), version 5. A total of 77 patients with VS were identified, of which 50 had FSRT and 27 had SRS. In the FSRT group, the median patient age was 58 years (range 23-81) and 50% were female, whereas the median patient age was 68 years (range 24-90) and 41% females were in the SRS group. 81% (n = 35) patients in the FSRT group and 24% (n = 6) in the SRS group had serviceable hearing prior to RT. Median follow-up was 51.2 months (range 4.3-103.2) in the FSRT group and 21.0 months (range 2.7-98.6) in the SRS group. The 2-year, 3-year, and 5-year local control rates in the FSRT and SRS groups were 100% and 100%, 97% and 76%, 94% and 76%, respectively. Of those with local progression, 33% (n = 1) in the FSRT group was salvaged with stereotactic body radiation therapy (SBRT) and 100% (n = 2) in the SRS group was salvaged with FSRT. For patients with serviceable hearing prior to RT, hearing preservations rates were 46% and 17% with a median time to hearing loss of 8.2 months (range 4.0-59.5) and 7.7 months (range 2.0-11.9) in the FSRT and SRS groups, respectively. Progression-free survival analyses showed superior hearing preservation in those treated with FSRT compared to SRS (p-value = 0.0064), especially those receiving FSRT who initially presented with GR1 vs GR2 hearing (p-value = 0.0095). There were 60 reported toxicities with 12% (n = 7) Grade 2+ in the FSRT group, whereas the SRS group had 5 toxicities with 40% (n = 2) Grade 2+. Both FSRT and SRS provide favorable local control for VS, with most progressions salvageable. Hearing preservation rate is higher in the FSRT group. This favors the use of FSRT in those with serviceable hearing, with patients with baseline GR1 hearing demonstrating additional benefit. Further prospective randomized studies are needed to better identify treatment outcomes and prognostic factors.