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TU_33_3013 - Salvage Gamma Knife Radiosurgery following First Treatment: Impact of Relevant Clinical Variables, MRI Features and Dose

Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3

Salvage Gamma Knife Radiosurgery following First Treatment: Impact of Relevant Clinical Variables, MRI Features and Dose
B. Foster1, P. P. Koffer1, J. E. Mignano1, and J. K. Wu2; 1Tufts Medical Center, Department of Radiation Oncology, Boston, MA, 2Tufts Medical Center, Department of Neurosurgery, Boston, MA

Purpose/Objective(s): Stereotactic radiosurgery (SRS) is an accepted treatment for refractory trigeminal neuralgia (TN) after SRS but outcomes are variable. Clinical, radiologic or dosimetric factors predictive of outcomes remain elusive. We hypothesized that pre-second SRS clinical, MRI and dosimetric factors would influence efficacy and toxicity.

Materials/Methods: Medical records from 1/2000 to 8/2017 were queried, identifying 118 patients receiving second SRS. Pre-treatment clinical and MRI data were collected. Statistics software calculated chi-square tests or binary logistic regressions for categorical or continuous variables, respectively.

Results: Fifty-nine patients undergoing second SRS had available follow-up (median 18 months [m], range 1.2 – 156.4 m). Median first SRS dose was 85 Gy and second SRS dose was 75 Gy (40 – 75 Gy). Median age was 69 years. Seven had bilateral TN and 6 had multiple sclerosis (MS). Pain recurred after second SRS in 35/59 (59.3%) at a median 12.2 m (no relief – 156 m). With at least 2 years follow-up, 69.2% (18/26) experienced recurrence. Fifty-five (93.2%) achieved BNI pain scale I-III (good pain outcome) at any point, with a median 2 m (range 0 days – 41 m) time to maximum (max) pain relief. At last follow-up, 12 no longer required meds and 36 had pain control +/- meds (BNI I-III). Facial numbness (FN) occurred in 26 (44%), being bothersome for 7 (11.8%). Dysguesia, paresthesia, masticator weakness (MW) and xerophthalmia were reported in 2 (8.4%), 6 (10.2%), 2 (8.4%) and 6 (10.2%) patients; respectively. MRI report of vessels near the affected nerve (TNe) was associated with max pain relief within 3 m (p=0.048, 16/27 with vs 3/12 without vessel). Reported contact between vessels and the TNe was associated with dysguesia (p=0.019, 0/40 without and 2/13 with contact) and paresthesia (p=0.022, 2/38 without and 4/11 with contact). A mass described near the TNe was correlated with MW (p<0.001, 1/2 with and 1/53 without a mass) and decreased need for meds at last follow-up (p=0.001, 2/2 with and 7/46 without a mass). No patients with MS developed new FN (p=0.022, 0/6 with MS vs 26/53 other); MS was not associated with other toxicities. Age, time from initial symptoms, and time to max pain relief were not associated with pain recurrence (p=0.730, 0.245 and 0.527). Prolonged pre-initial SRS symptoms were associated with FN (p=0.025). Low repeat dose (< 70 Gy) and cumulative dose (< 130 Gy) were associated with developing MW (p=0.015 2/14 vs 0/40 in high dose) but, contrary to prior reports, not with recurrence, time to pain relief or other toxicities.

Conclusion: Most patients undergoing repeat SRS will experience improvement within at least 1 year and achieve pain control with or without meds (BNI I-III). Toxicity rates among this group are acceptable and generally tolerable. Several MRI features are associated with clinically significant toxicities and warrant further investigation.

Author Disclosure: B. Foster: None. P.P. Koffer: None. J.E. Mignano: None. J.K. Wu: None.

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