RTOG 0631 Phase II/III Study of Image-Guided Stereotactic Radiosurgery for Localized (1-3) Spine Metastases: Phase II Results.

PURPOSE: The phase II component of RTOG 0631 assessed the feasibility and safety of spine radiosurgery (SRS) for localized spine metastases in a cooperative group setting. MATERIALS AND METHODS: Patients with 1-3 spine metastasis with a Numerical Rating Pain Scale (NRPS) score ≥ 5 received 16 Gy single fraction SRS. The primary endpoint was SRS feasibility: image-guidance RT (IGRT) targeting accuracy ≤ 2mm, target volume coverage > 90% of prescription dose, maintaining spinal cord dose constraints (10 Gy to ≤ 10% of the cord volume from 5-6mm above to 5-6mm below the target or absolute spinal cord volume < 0.35cc) and other normal tissue dose constraints. A feasibility success rate < 70% was considered unacceptable for continuation of the phase III component. Based on the one-sample exact binomial test with α=0.10 (1-sided), 41 patients were required. Acute toxicity was assessed using the National Cancer Institute Common Toxicity Criteria for Adverse Events, version 3.0. RESULTS: Sixty-five institutions were credentialed with spine phantom dosimetry and IGRT compliance. Forty-six patients were accrued, and 44 were eligible. There were 4 cervical, 21 thoracic and 19 lumbar sites. Median NRPS was 7 at presentation. Final pre-treatment rapid review was approved in 100%. Accuracy of image-guided SRS targeting was in compliance with the protocol in 95%. The target coverage and spinal cord dose constraint were in accordance with the protocol requirements in 100% and 97%. Overall compliance for other normal tissue constraints was per protocol in 74%. There were no cases of grade 4-5 acute treatment-related toxicity. CONCLUSION: The phase II results demonstrate the feasibility and accurate use of SRS to treat spinal metastases, with rigorous quality control, in a cooperative group setting. The planned RTOG 0631 phase III component will proceed to compare pain relief and quality of life between SRS and external beam radiotherapy.

Duke Scholars

Author Fang-Fang Yin Radiation Oncology