Radiosurgery Outcomes in Vestibular Schwannoma: Effect of New Technologies

To assess whether improved technology of radiosurgery (RS) results in better local control and long-term outcomes in the treatment of vestibular schwannoma (VS). A retrospective analysis was performed of 165 consecutive patients harboring 167 tumors, treating 151 patients (90.5%) with stereotactic radiosurgery (SRS) and 16 patients (9.5%) using fractionated stereotactic radiation therapy (FSRT). Two phases in the treatment of RS were analyzed: the first phase (P1), from 1997 to 2005, used conical collimators, adapted to a linear accelerator, 3D planification system, and 6 MV photons with Arctherapy technique. During the second phase (P2), from 2005 onwards, BrainLAB® technology with stereotactic frame, Brainscan 3.5 planner, M3 collimator, adapted to a linac was used. The margin dose was 12 Gy for RS. Ten fractions of 3 Gy, or 28 fractions of 1.8 Gy were delivered for FSRT. Clinical local control was defined as the absence of other treatments. Statistical analysis was performed. A total of 103 tumors were treated during P1 and 64 lesions during P2. Mean follow-up was 9.3 ± 0.4 years for the P1 and 2.4 ± 0.5 years for P2. The mean age was 58.4 ± 2 years. No statistically significant differences were found at outcomes between phases. Tumor staging following Koos’ classification was Type I, 15% in P1 vs 21% in P2, Type II: 48% vs 55%, type III: 21% vs 19%, type IV: 16% vs 5%. One hundred forty-five tumors (86%) were exclusively radiated, and 22 (14%), were treated with combination of surgery and radiation therapy. Local control rates for P1 were 96%, 95% and 95% at 5, 10, and 15 years, respectively. The P2 achieved 100% local control at 5 years. We observed tumor growth in 24 patients (14.5%), but only five of them required surgery, exclusively at P1. The remaining 19 patients were considered as transient swelling. Facial nerve neuropathy rates were 4% (P1) vs 8% (P2). Permanent facial palsy occurred only at P1 in 1.2%. Hearing preservation was 60% in P1 vs 76.4% at P2. In 22 patients with large tumors (>30 mm largest diameter), local control was 91% at 5, 10, and 15 years with RS, while FSRT (only at P2) achieved a 100% control. Tumor mortality was 4.8%, only at P1, due to tumor growth or complications related to rescue surgery. Cause-specific survival was 97% at 5 year and 95% at 10 and 15 years in P1, and 100% in the P2. At current follow-up, there is no statistically significant technical superiority at observed outcomes. However, there is a clear trend toward improved local control and long-term outcomes in the second phase with better and newer technology.