SU‐F‐T‐647: Linac‐Based Stereotactic Radiosurgery (SRS) in the Treatment of Trigeminal Neuralgia: Detailed Description of SRS Procedural Technique and Reported Clinical Outcomes

Abstract

Purpose:SRS is an effective non‐invasive alternative treatment modality with minimal‐toxicity used to treat patients with medically/surgically refractory trigeminal neuralgia root(TNR) or those who may not tolerate surgical intervention. We present our linac‐based SRS procedure for TNR treatment and simultaneously report our clinical outcomes.Methods:Twenty‐eight TNR‐patients treated with frame‐based SRS at our institution (2009–2015) with a single‐fraction point‐dose of 60‐80Gy to TNR were included in this IRB‐approved study. Experienced neurosurgeon and radiation oncologist delineated the TNR on 1.0mm thin 3D‐FIESTA‐MRI that was co‐registered with 0.7mm thin planning‐CT. Treatment plans were generated in iPlan (BrainLAB) with a 4‐mm diameter cone using 79 arcs with differential‐weighting for Novalis‐TX 6MV‐SRS(1000MU/min) beam and optimized to minimize brainstem dose. Winston‐Lutz test was performed before each treatment delivery with sub‐millimeter isocenter accuracy. Quality assurance of frame placement was maintained by helmet‐bobble‐measurement before simulation‐CT and before patient setup at treatment couch. OBI‐CBCT scan was performed for patient setup verification without applying shifts. On clinical follow up, treatment response was assessed using Barrow Neurological Institute Pain Intensity Score(BNI‐score:I–V).Results:26/28 TNR‐patients (16‐males/10‐females) who were treated with following single‐fraction point‐dose to isocenter: 80Gy(n=22),75Gy(n=1),70Gy(n=2) and 60Gy(n=1, re‐treatment) were followed up. Median follow‐up interval was 8.5‐months (ranged:1–48.5months). Median age was 70‐yr (ranged:43–93‐yr). Right/left TNR ratio was 15/11. Delivered total # of average MUs was 19034±1204. Average beam‐on‐time: 19.0±1.3min. Brainstem max‐dose and dose to 0.5cc were 13.3±2.4Gy (ranged:8.1–16.5Gy) and 3.6±0.4Gy (ranged:3.0–4.9Gy). On average, max‐dose to optic‐apparatus was ≤1.2Gy. Mean value of max‐dose to eyes/lens was 0.26Gy/0.11Gy. Overall, 20‐patients (77%) responded to treatment: 5(19%) achieved complete pain relief without medication (BNI score: I); 5(19%) had no‐pain, decreased medication (BNI‐score:II); 2(7.7%) had no‐pain, but, continued medication (BNI‐score:IIIA), and 8(30.8%) had pain that was well controlled by medication (BNI‐score: IIIB). Six‐patients (23.0%) did not respond to treatment (BNI‐score:IV–V). Neither cranial nerve deficit nor radio‐necrosis of temporal lobe was clinically observed.Conclusion:Linac‐based SRS for medically/surgically refractory TNR provided an effective treatment option for pain resolution/control with very minimal if any normal tissue toxicity. Longer follow up of these patients is anticipated/needed to confirm our observations.