2556 - Repeat Stereotactic Body Radiotherapy (SBRT) for Spinal Metastases: Local Control and Toxicity
Presenter(s)
S. Adida1, S. Taori1, S. Choi2, T. McCaw2, S. A. Burton2, J. C. Flickinger Sr2, R. K. Sefcik3, and P. C. Gerszten1; 1Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, 2Department of Radiation Oncology, UPMC Hillman Cancer Center, Pittsburgh, PA, 3Department of Neurosurgery, Medical University of South Carolina, Charleston, SC
Purpose/Objective(s): Stereotactic body radiotherapy (SBRT) is an effective salvage therapy for previously irradiated spinal metastases following external beam radiation therapy (EBRT). This study is the largest to report outcomes after a second course of SBRT following SBRT local failure (LF) in patients with spinal metastases.
Materials/Methods: A prospectively maintained single-institution database of patients treated with spine SBRT from 2002 to 2023 was analyzed. Inclusion criteria consisted of patients with spinal metastases who underwent a second course of SBRT for LF after an initial course of SBRT. Patients who underwent open surgical intervention before the salvage second course of SBRT were excluded. The median dose for salvage SBRT was 16 Gy (range: 12-30) in 1 fraction (range: 1-3 fractions; median biologically effective dose (BED10): 41.6 Gy, range: 26.4-60).
Results: Fifty-five patients with 67 metastases met inclusion criteria. Fifty-four (81%) metastases received EBRT before the initial course of SBRT. The median duration between the initial and salvage courses was 8 months (range: 2-125). After a median follow-up of 8 months (range: 1-167), rates of 6-month, 1-year, and 2-year local control (LC) were 96%, 85%, and 77%, respectively. Univariable analysis revealed that prior EBRT (p = 0.014, HR: 0.13, 95% CI: 0.02-0.66) was significantly associated with superior LC. Patient age and sex, functional status, tumor burden and volume, BED10, Epidural Spinal Cord Compression scores, Spinal Instability Neoplastic Scores, and multilevel tumors were not associated with LC. Rates of 6-month, 1-year, and 2-year overall survival (OS) were 69%, 53%, and 35%, respectively. Univariable analysis identified age = 65 years (p = 0.036, HR: 1.74, 95% CI: 1.04-2.93) and Karnofsky Performance Score > 70 (p = 0.038, HR: 0.57, 95% CI: 0.33-0.97) as associated with superior OS. On multivariable analysis, no factors remained associated with OS. Clinical improvement or stability of pain was observed after 95%, 82%, and 75% of treatments at 3, 6, and 12 months, respectively. Fifteen radiation-induced toxicities (22%) were identified, including 9 radiation-induced vertebral compression fractures (13%, VCFs) occurring a median of 9 months (range: 2-13) after treatment (4 de novo fractures, 6%; 5 progressive fractures, 7%). Accounting for the competing risk of death, the 6-month, 1-year, and 2-year VCF rates were 94%, 77%, and 72%, respectively. No grade 4 or 5 late toxicities were observed, and no radiation-induced neuropathy or myelopathy was reported.
Conclusion: A second course of SBRT following SBRT LF achieves durable LC and pain relief with acceptable toxicity rates in patients with progression of spinal metastases, even in heavily pretreated patients previously irradiated with EBRT.