Long-term Outcomes After Stereotactic Radiosurgery for Spine Metastases: Radiation Dose-Response for Late Toxicity

Publication date: Available online 6 March 2018
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Diane C. Ling, John C. Flickinger, Steven A. Burton, Dwight E. Heron, Annette E. Quinn, Ghassan K. Bejjani, Johnathan A. Engh, Peter C. Gerszten, Nduka M. Amankulor, John A. Vargo
BackgroundWhile a large body of data supports the safety and efficacy of stereotactic radiosurgery (SRS) for the primary treatment and re-irradiation of spine metastases, concerns over late toxicity inherent to hypofractionation remain, as follow-up in most series is limited to 1-2 years.MethodsA retrospective review was performed on 562 patients treated with SRS for spine metastases between April 2001 and July 2011. Selecting those with at least 5-year survival after SRS, included were 43 patients who collectively underwent 84 treatments at 54 spine sites. Most were treated with single-fraction SRS to a median dose of 16Gy (range: 12-24), and 56% of sites had received prior external beam radiation therapy. Late toxicities and vertebral compression fractures (VCF) occurring in the absence of tumor progression were recorded. Binary logistic regression was used to identify predictors of late complications.ResultsNine patients (17% of treatment sites) developed grade ≥2 late toxicities at a median time of 12.8 months (range: 4.2-59.0). Actuarial 5- and 10-year rates of grade ≥2 late toxicity were 17% and 17%, respectively. On multivariate analysis, only cumulative BED3 >200Gy (or EQD22Gy >130Gy) was associated with grade ≥2 late toxicity (p=0.036). Maximum point BED3 >110Gy (or EQD22Gy >70Gy) to spinal cord or cauda equina was associated with grade ≥2 late neuropathy (p=0.017). Nine (18%) VCFs occurred at a median time of 10.2 months (range: 3.2-57.2), with 5- and 10-year VCF rates of 17% and 17%, respectively.ConclusionSRS for primary treatment and re-irradiation of spinal metastases is associated with a moderate risk of late toxicity with 10-year follow-up. Risk of late toxicity significantly increases with cumulative BED3 >200Gy and spinal cord or cauda equina point BED3 >110Gy. Patients remain at moderate risk of VCF up to 5-years following treatment, with a plateau in incidence thereafter up to 10 years.



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