Outcomes of stereotactic radiosurgery for spine multiple myeloma-a systematic review.
Spinal involvement in multiple myeloma (MM) commonly results in pain, vertebral instability, epidural spinal cord compression, and neurological deficits. Although conventional external beam radiation therapy (EBRT) remains the standard radiation modality because of the radiosensitive nature of MM, stereotactic radiosurgery (SRS) has emerged as a highly conformal treatment option capable of delivering focal high-dose radiation while sparing adjacent spinal cord structures and uninvolved bone marrow. This systematic review evaluated the clinical outcomes and safety profile of SRS for spinal MM. A systematic review of the literature was performed to identify studies evaluating SRS for spinal MM. Extracted variables included patient demographics, tumor characteristics, treatment parameters, radiographic outcomes, pain response, neurological outcomes, local control, overall survival, and adverse events. Three retrospective studies comprising 133 patients and 181 treated spinal lesions met the inclusion criteria. Median patient age ranged from 59 to 65 years, with a slight male predominance across studies. Thoracic spine lesions represented the most treated region (55.5-67.7%). Median prescribed SRS dose was 14-16 Gy, predominantly delivered in a single fraction. Median follow-up ranged from 11.2 to 27.8 months. Local control rates ranged from 89.4 to 100%, with 6- and 12-month local control rates of 94% and 91%, respectively, in one study. Pain improvement was reported in 41-88% of treated patients/sites, with a median time to pain relief of 1.6 months in one cohort. Neurological improvement occurred in 56-71.4% of patients with preexisting deficits. Reported adverse events included vertebral compression fractures, fracture progression, pain flare, and tracheoesophageal fistula. De novo vertebral fractures ranged from 3.6 to 7%, while fracture progression ranged from 14 to 18%. SRS appears to provide excellent local control and meaningful pain and neurological improvement in patients with spinal MM, with acceptable toxicity profiles. The highly conformal nature of SRS may preserve uninvolved bone marrow and facilitate continuation of systemic therapy. However, the current evidence is limited to small retrospective studies with heterogeneous reporting, and further prospective comparative studies are needed to better define the role of SRS relative to conventional EBRT in spinal MM.