Central Nervous System

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MO_12_2778 - Stereotactic Body Radiation Therapy is an Effective and Safe Treatment for Benign Spinal Tumors

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Stereotactic Body Radiation Therapy is an Effective and Safe Treatment for Benign Spinal Tumors
S. A. Lloyd1, G. B. Encouse1, A. J. Clark2, M. W. McDermott2, and S. E. Braunstein3; 1University of California San Francisco, Department of Radiation Oncology, San Francisco, CA, 2University of California San Francisco, Department of Neurological Surgery, San Francisco, CA, 3University of California, San Francisco, San Francisco, CA

Purpose/Objective(s): Primary spinal tumors are rare (<5% of CNS tumors), with two thirds being benign. Benign spinal tumors (BSTs) may not have malignant biology, but they can produce mass effect on nearby neurologic structures, resulting in potentially devastating neuropathies and myelopathies. Historically, resection of BSTs has been preferred; however, tumor location, recurrent disease, or patient factors may preclude surgical management. Advances in image guidance and immobilization have established SBRT as a feasible alternative and/or complement to surgery. We examined our institution’s experience to determine the safety and efficacy of SBRT for BSTs.

Materials/Methods: We conducted a single institution, retrospective review of 21 patients with 23 BSTs treated with SBRT. Toxicities (graded by CTCAE v4.0) and responses (symptomatic and radiographic) were documented and reported with descriptive statistics and univariate analysis (chi-square and logistic regression).

Results: Median age was 58 (rng: 31-81), with 29% male, 71% female, and median KPS 90 (IQR: 70-90). Histology (biopsy or imaging) was 43% meningioma, 35% schwannoma, 13% hemangioma, and 9% other. Spinal level was 43% cervical, 26% thoracic, 17% lumbar, and 14% sacral. SBRT was 57% definitive, 22% adjuvant (following STR), 17% for recurrence, and 4% pre-operative. 52% of lesions had prior resection, while 0% had prior RT. Presenting symptoms included 57% pain, 48% paresthesias, 24% weakness, and 24% asymptomatic. SBRT delivery was 57% VMAT or 43% robotic. Median prescription dose was 25 Gy (rng: 18-40) in 5 fx (rng: 3-5) with median isodose of 84% (IQR: 74-91). Median PTV was 5.9 cc (IQR: 3.2-18.2). Median Min/Mean/Max PTV dose was 23.4/27.0/29.4 Gy. Median follow-up was 25 mo (rng: 2-80) with 2 unrelated deaths. Imaging was obtained every 3-6 mo. Symptomatically, 30% of patients improved, while 65% remained stable. Radiographically, 11% of lesions decreased in size, while 84% remained stable. 1 patient had symptomatic and radiographic failure of SBRT (for prior STR of schwannoma). Early AEs (<6 mo) occurred in 8/21 (38%) patients. There were 6 patients with pain flare, 4 with fatigue (all ≤grade 2). Late AEs (>6 mo) occurred in 2/21 (9.5%) patients (1 patient with grade 2 radiation-induced myelitis, 1 patient with grade 1 paresthesias) that received surgery either before or after SBRT for spinal meningioma and hemangioma, respectively. Response and toxicity were independent of tumor location, modality, PTV, and dose on univariate analysis.

Conclusion: Consistent with prior reports, we found SBRT to be an effective and well-tolerated treatment for BSTs, with 95% of lesions controlled symptomatically and/or radiographically. Acute pain flare was the most common AE, although responsive to short-course steroids. Premedication or spaced treatment may be considered to reduce acute toxicity. Pre/post-op SBRT may increase risk of AEs, as surgical instrumentation may sensitize the spinal cord to radiation-induced injury.

Author Disclosure: S.A. Lloyd: None. G.B. Encouse: None. M.W. McDermott: None. S.E. Braunstein: Advisory Board; Radiation Oncology Questions, LLC.

Shane Lloyd, MD, PhD

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