Stereotactic spine radiosurgery: Review of safety and efficacy with respect to dose and fractionation

Abstract

Background:Stereotactic body radiotherapy (SBRT) is an emerging treatment option for spinal metastases with demonstrated efficacy in the upfront, postoperative, and re-treatment settings, as well as for tumor histologies considered radioresistant. Uncertainty exists regarding the optimal dose and fractionation schedule, with single and multifraction regimens commonly utilized.Methods:A literature search of the PubMed and Medline databases was conducted to identify papers specific to spine SBRT and the effect of varying dose/fractionation regimens on outcomes. Bibliographies of relevant papers were searched for further references, and international spine SBRT experts were consulted.Results:Local control rates generally exceed 80% at 1 year, while high rates of pain control have been attained. There is insufficient evidence to suggest superiority of either single or multiple fraction regimens with respect to local control and pain control. Low rates of toxicity have been reported, assuming strict dose constraints are respected. Radiation myelopathy may be the most morbid toxicity, although the rates are low. The risk of vertebral compression fracture appears to be associated with higher doses per fraction such as those used in single-fraction regimens. The Spinal Instability Neoplastic Score should be considered when evaluating patients for spine SBRT, and prophylactic stabilisation may be warranted. Pain flare is a relatively common toxicity which may be mediated with prophylactic dexamethasone. Because of the treatment complexity and potentially serious toxicities, strict quality assurance should occur at the organizational, planning, dosimetric, and treatment delivery levels.Conclusion:Both single and multifraction regimens are safe and efficacious in spine SBRT for spinal metastases. There may be advantages to hypofractionated treatment over single-fraction regimens with respect to toxicity. Ongoing investigation is underway to define optimal dose and fractionation schedules.

Outcomes in the radiosurgical management of metastatic spine disease

“…However, more, preferably prospective, data are clearly needed to adequately address these questions. 27 …”

“…Indeed, total dose and fractionation have been reported to correlate with an increased risk of fracture, with high-dose single-fraction treatment carrying the greatest risk. 27 Fracture rates approaching 40% have occurred with doses of 24 Gy in a single fraction delivered to the 100% isodose line. 39 …”

Frequency of Large Intrafractional Target Motions During Spine Stereotactic Body Radiation Therapy

“…Of the 366 sites treated, 96 were at levels T4 and superiorly, 270 were at levels T5 and inferiorly. To improve patient comfort, 17,18 all patients were set up with arms down at the sides or, if the target was inferior of the elbows, crossed over the chest and with the knees raised with a cushion.…”

Local failure and vertebral body fracture risk using multifraction stereotactic body radiation therapy for spine metastases

“…and Redmond et al., which concluded that there is currently no evidence to suggest that LC is superior with either single fraction or multifraction SBRT. 19 , 20 …”