Objective: Primary thyroid cancer metastasizing to the spine portends poor survival and low quality of life. Current management strategies continue to evolve. This single-institution retrospective study analyzes outcomes after spinal stereotactic radiosurgery for patients with spinal metastases from thyroid cancer.
Methods: Nineteen patients (median age: 64.5 years) were treated with stereotactic radiosurgery (SRS) for spinal primary thyroid metastases (40 metastases, 47 vertebral levels) between 2003 and 2023. Nineteen (47.5%) lesions had epidural involvement and 20 (50%) lesions were classified as potentially unstable or unstable via the Spinal Instability Neoplastic Score. The median tumor volume per lesion was 33 cc (range: 1.5-153). The median single fraction prescription dose was 20 Gy (range: 12-23.5).
Results: The median follow-up period was 15 months (range: 2-40). Five (12.8%) lesions locally progressed at a median of 9 months (range: 4-26) after SRS. The 1-, 2-, and 3-year local tumor control rates per lesion were 90.4%, 83.5%, and 75.9%, respectively. On univariate analysis, age at SRS >70 years (P = 0.05, hazard ratio: 6.86, 95% confidence interval: 1.01-46.7) was significantly correlated with lower rates of local tumor control. The median overall survival was 35 months (range: 2-141). The 1-, 2-, and 3-year overall survival rates were 73.7%, 50.4%, and 43.2%, respectively. For 33 lesions initially associated with pain, patients reported pain improvement (22 lesions, 66.7%), stability (10 lesions, 30.3%), and worsening (1 lesion, 3.0%) after SRS. One patient developed dysphagia 4 months after SRS treatment.
Conclusions: SRS can be utilized as an effective and safe primary and adjuvant treatment option for primary thyroid metastases to the spine.
Keywords: Local tumor control; Primary thyroid cancer; Radiation-induced toxicity; Spine metastases; Spine stereotactic radiosurgery.
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