The Role of Stereotactic Radiosurgery for Patients with Spinal Metastases from Primary Prostate Cancer

Introduction: Prostate cancer metastases to the spine can result in significant morbidity, intractable pain, and mechanical instability. This study involved a review of a consecutive series of patients treated with stereotactic radiosurgery (SRS) for spine metastases from prostate cancer.

Methods: Thirty-seven patients (51 lesions, 75 vertebral levels) were treated with SRS for prostate cancer spine metastases from 2003-2022. The median age at SRS was 72 years (range: 52-94), and the median KPS at SRS was 80 (range: 60-100). Fifteen (29.4%) lesions were treated with prior surgical resection, while 34 (66.7%) lesions underwent prior conventional external beam radiotherapy. The median Spinal Instability Neoplastic Score (SINS) was 7 (range: 1-13), and 9 lesions (17.6%) had epidural involvement. The median tumor volume was 37 cc (range: 2.9-263.3 cc), and the median prescription dose was 20 Gy (range: 12-22.5). Fifteen (29.4%) lesions were treated with multi-fraction SRS.

Results: The median follow-up period was 12 months. The 1- and 3-year local tumor control rates were both 91%. The median overall survival was 17 months. The 1- and 3-year overall survival rates were 56.2% and 32.0%, respectively. On multivariate analysis, both age at SRS > 70 years (P=0.048, HR: 2.38, 95% CI: 1.01-5.63) and total tumor volume > 30 cc (P=0.03, HR: 3.85, 95% CI: 1.12-13.2) were significantly correlated with inferior rates of overall survival. For 48 lesions initially associated with pain, patients reported improvement in pain for 30 lesions (62.5%) and stable pain for the remaining 18 lesions (37.5%). Three (5.9%) lesions locally progressed at a median time of 8 months (range: 3-9) after SRS and were all successfully re-treated with repeat SRS. No patients experienced radiation toxicity or symptomatic vertebral compression fracture following SRS treatment.

Conclusion : Prostate cancer spinal metastases may be associated with significant morbidity. Spine SRS can be utilized as a successful treatment strategy to provide excellent long-term local tumor control and improve pain-related symptoms.