1 From Benign CNS SRS Therapy to SRS Treatments for Facetogenic Pain: Extrapolating SafetyDavid Zaenger MDa, Raymond Schulz, MScb, Bryan M. Rabatic PhD MDa, Waleed F. Mourad MD PhDa, John R. Vendera, Joseph Kaminski MDa aGeorgia Regents University bVarian Medical Systems Clinical Problem Results SRS Advantages/Disadvantages SRS advantages Non-invasive Painless Increasingly Accessible Possible ablative and anti-inflammatory effects Disadvantages Ability to retreat is limited Potential adverse effects of radiation Stigma of radiation Unknowns Idea Target (PTV) Optimal Dose Duration of response Cost-effectiveness Is Stereotactic Radiosurgery (SRS) safe to treat benign facetogenic lower back pain? In non-oncologic patients with facetogenic lower back pain, does SRS cause radiation-induced malignancies and/or radiation-induced myelopathy? With over 1,000,000 cranial cases treated to date, radiation- induced malignancy from SRS is very rare with less than 40 cases in the literature, spanning > 30 years and > 5000 papers. Several recent large respective studies with long-term follow-up failed to demonstrate any conclusive increase risk after intracranial SRS. Additionally, prior experience demonstrates that spinal radiation can be delivered with minimal risk of radiation-induced myelopathy. Conclusion Background Although more study is needed, it seems the risk of radiation- induced malignancy and radiation-induced myelopathy from SRS is very low. As such, SRS is likely safe to be used for medically refractory facetogenic pain. We are currently exploring the potential role of radiosurgery to treat facetogenic pain and are planning a prospective phase I/II study. Risk could further be minimized by selecting patients above the age 55 and targeting facet joints below the conus-medullaris. Proposed Protocol Chronic lower back pain secondary to facetogenic is a prevalent debilitating disease accounting for 15-45% of chronic lower back pain which decreases a person’s quality of life and negatively impacts the economy. The first line of treatment is conservative therapy with medications and physical therapy. For those that fail conservative therapy (i.e., medically refractory pain), the primary treatment is percutaneous injections and/or radiofrequency ablation. However, there is much room for improvement in the current treatment paradigm as many patients are either not candidates for percutaneous interventions or fail to get adequate relief. Given radiosurgery’s success in treating other benign pain syndromes (e.g., trigeminal neuralgia), there has been interest in radiosurgical rhizotomy for facetogenic back pain. Identify qualifying patients from referral. Step 1 CT simulation and Immobilization Step 2 Co-register MRI and SRS treatment planning Step 3 Single Session SRS to diseased facet joint Step 4 Discussion Many patients fail conservative treatments with medication and physical therapy and have medically refractory facetogenic pain. The current treatment paradigm for medically refractory pain primarily consists of percutaneous injections and radiofrequency ablation. However, the data supporting percutaneous interventions is limited. Furthermore, some patients either are not candidates for invasive procedures, or do not get satisfactory relief. As noted previously, the potential risks of SRS can be mitigated. For example, selecting patient over the age of 55 reduces the risk of radiation-induced malignancy. Also, targeting facet joints below the conus minimizes the risks of radiation-induced myelopathy. To date, there is only one trial of 5 patients from 2007 which examined this topic. Although the results were promising, a larger series with more follow-up is needed. Thus, our institution is planning a prospective phase I/II protocol to study the safety and efficacy of SRS for medically refractory facetogenic back pain. Works Cited Objective Boswell, M. V., J. D. Colson, N. Sehgal, E. E. Dunbar and R. Epter (2007). "A systematic review of therapeutic facet joint interventions in chronic spinal pain." Pain Physician 10(1): Chou, R., S. J. Atlas, S. P. Stanos and R. W. Rosenquist (2009). "Nonsurgical interventional therapies for low back pain: a review of the evidence for an American Pain Society clinical practice guideline." Spine (Phila Pa 1976) 34(10): Cohen, S. P. and S. N. Raja (2007). "Pathogenesis, diagnosis, and treatment of lumbar zygapophysial (facet) joint pain." Anesthesiology 106(3): Degen, J. W., G. J. Gagnon, J. M. Voyadzis, D. A. McRae, M. Lunsden, S. Dieterich, I. Molzahn and F. C. Henderson (2005). "CyberKnife stereotactic radiosurgical treatment of spinal tumors for pain control and quality of life." J Neurosurg Spine 2(5): Gaskin, D. J. and P. Richard (2012). "The economic costs of pain in the United States." J Pain 13(8): Gibbs, I. C., C. Patil, P. C. Gerszten, J. R. Adler, Jr. and S. A. Burton (2009). "Delayed radiation-induced myelopathy after spinal radiosurgery." Neurosurgery 64(2 Suppl): A67-72. Gorgulho, A. (2013). Role of Radiosurgery for Trigeminal Neuralgia. Handbook of Radiosurgery in CNS Disease. M. Lim. New York, Demos Medical Publishing, LCC: Katz, J. N. (2006). "Lumbar disc disorders and low-back pain: socioeconomic factors and consequences." J Bone Joint Surg Am 88 Suppl 2: Kornick, C., S. S. Kramarich, T. J. Lamer and B. Todd Sitzman (2004). "Complications of lumbar facet radiofrequency denervation." Spine (Phila Pa 1976) 29(12): Li, G., C. Patil, J. R. Adler, S. P. Lad, S. G. Soltys, I. C. Gibbs, L. Tupper and M. Boakye (2007). "CyberKnife rhizotomy for facetogenic back pain: a pilot study." Neurosurg Focus 23(6): E2. Marchetti, M., E. De Martin, I. Milanesi and L. Fariselli (2013). "Intradural extramedullary benign spinal lesions radiosurgery. Medium- to long- term results from a single institution experience." Acta Neurochir (Wien) 155(7): Patel, T. R. and V. L. Chiang (2014). "Secondary neoplasms after stereotactic radiosurgery." World Neurosurg 81(3-4): Rahman, M., D. Neal, W. Baruch, F. J. Bova, B. H. Frentzen and W. A. Friedman (2014). "The Risk of Malignancy Anywhere in the Body after Linear Accelerator (LINAC) Stereotactic Radiosurgery." Stereotact Funct Neurosurg 92(5): Rowe, J., A. Grainger, L. Walton, P. Silcocks, M. Radatz and A. Kemeny (2007). "Risk of malignancy after gamma knife stereotactic radiosurgery." Neurosurgery 60(1): 60-65; discussion Ryu, S., R. Jin, J. Y. Jin, Q. Chen, J. Rock, J. Anderson and B. Movsas (2008). "Pain control by image-guided radiosurgery for solitary spinal metastasis." J Pain Symptom Manage 35(3): Saraceni, C., J. B. Ashman and J. S. Harrop (2009). "Extracranial radiosurgery--applications in the management of benign intradural spinal neoplasms." Neurosurg Rev 32(2): ; discussion Our objective to review the risk of radiation-induced malignancy and radiation-induced myelopathy from the benign SRS experience to evaluate the potential safety of radiosurgery for medically refractory facetogenic pain. Methods & Materials The PubMed® database was searched using various combinations of the key words including stereotactic radiosurgery, radiosurgery, facet pain, facetogenic pain, trigeminal neuralgia, spinal radiosurgery, radiation-induced myelopathy, and radiation-induced malignancy. The relevant literature was selected for review and analysis.