Linear accelerator-based flattening-filter-free stereotactic radiosurgery for trigeminal neuralgia: Feasibility and patient-reported outcomes.

Abstract

The purpose of this study was to assess the safety and outcomes of the clinical use of LINAC (linear accelerator)-based flattening-filter-free beams for delivering ablative stereotactic radiosurgery (SRS) for trigeminal neuralgia (TN). Thirty-six consecutive patients (34 unique patients) followed up by a single neurosurgeon and diagnosed with medically refractory unilateral TN were treated with SRS. There were 14 left-sided cases (41%) and 20 right-sided cases (59%). Twenty-eight of the patients (82%) had type 1 TN, and 6 (18%) had type 2 TN. Previous treatments were as follows: 10 patients (29%) had SRS to the ipsilateral TN (8 with Gamma Knife, 2 with LINAC), 4 (12%) had percutaneous rhizotomy, and 3 (9%) had microvascular decompression. A median prescription dose of 75 Gy (range, 70-80 Gy), prescribed to the 100% isodose line, was delivered in a single fraction. Before treatment delivery, image guidance verified stereotactic frame placement, head position, and final isocenter. The volume of brainstem receiving ≥10 Gy was <0.5 cm(3). At each visit, patients prospectively reported outcomes using the Barrow Neurological Institute (BNI) pain scale. With a median follow-up of 3.1 months (range, 0.6-24.3; mean, 5.5 months), no patient experienced grade 1+ toxicities. There were no new episodes of dysesthesia, hypoesthesia, or long-term complications related to SRS. Median baseline (pre-SRS) BNI score was 5.0 (mean, 4.7). Clinical assessment at first follow-up (median, 1 month) demonstrated a median BNI score of 3.0 (mean, 3.1). When stratified by TN subtype, both type 1 and type 2 TN patients had a median BNI score of 3.0 at first follow-up. Thirty patients (88.2%) achieved a reduction in their BNI at their first follow-up, and 5 patients (15%) achieved a score <3, which represents medication-free pain relief. The median BNI at second follow-up (average, 6.3 months) was 2.5. We report our experience with modern LINAC-based SRS using flattening-filter-free beams for TN. This treatment appears to be a safe and effective technique, although longer follow-up is needed to confirm durability. This modality may prove to be a viable treatment alternative for TN.