Between January 1996 and December 2009, 158 acoustic neuromas were treated by FSR in 155 patients. They received a dose of 50.4 Gy, with a safety margin of 1-2 mm with a median tumor volume at 2.45 mL (range: 0.17-12.5 mL) and a median follow-up duration at 60 months (range: 24-192).
FSR was well tolerated in all patients with mild sequelae consisting in radiation-induced trigeminal nerve impairments (3.2 % ), Grade 2 facial neuropathies (2.5 % ), new or aggravated tinnitus (2.1 % ) and VP shunting (2.5 % ). The treatment failed in four patients (2.5 % ) who had subsequent surgery respectively at 20, 38, 45 and 84 months post-FSR. The local tumor control rates were respectively 99.3 % , 97.5 % and 95.2 % at 3, 5 and >7-year of follow-up. For initial Gardner-Robertson Grade 1 and 2 ANs, the preservation of useful hearing was possible in 54 % of the cases; only Grade 1 ANs had stabilized during the course of the follow-up with 71 % >7 years. However, hearing preservation was not correlated to the initial Koos Stage and to the radiation dose delivered to the cochlea. Tinnitus (70 % ), vertigo (59 % ), imbalance (46 % ) and ear mastoid pain (43 % ) had greatly improved post-FRS in most patients. Tumor control, hearing preservation and FRS toxicity were quite similar in patients with NF2, cystic acoustic neuroma, prior surgical resection and Koos Stage 4 AN. No secondary tumors were observed.
FSR is a safe and effective therapeutic for acoustic neuromas and could be an alternative to microsurgery. Compared to radiosurgery, there are no contraindications for fractioned doses of stereotactic radiotherapy especially for Stage-4 tumors and patients at high risk of hearing loss.