(S019) Prospective Evaluation of Stereotactic Radiosurgery for Spinal Metastases in the Postoperative Setting

Randa Tao, MD, Eva N. Christensen, MD, PhD, T. Jonathan Yang, MD, Patricia L. Grossman, Sr. Research Nurse, Paul D. Brown, MD, Stephen H. Settle, Jr, MD, Eric L. Chang, MD, Amit K. Garg, MD, Xin Wang, PhD, Laurence D. Rhines, MD, Amol J. Ghia, MD; UT MD Anderson Cancer Center

Background: Stereotactic body radiotherapy (SBRT) has emerged as an effective option in the treatment of metastatic spinal tumors. The technique achieves a steep dose gradient to deliver ablative doses to the tumor while sparing the adjacent spinal cord. Surgical resection is commonly followed by radiation to address residual microscopic disease. When SBRT is used in combination with a surgical approach, the potential for achieving durable symptom and tumor control may be possible for appropriately selected patients, but limited prospective data exist. The purpose of our study is to evaluate the outcomes of patients treated with SBRT in the postoperative setting.

Methods: The subset of patients who were enrolled in a prospective phase I–II study of SBRT for spinal metastasis treated after undergoing surgical management was included in this study. The initial patients enrolled on protocol were treated to 30 Gy in five fractions, which represented 13 of the 67 tumors treated, while the majority of the remaining tumors was treated to 27 Gy in three fractions. Patients were followed with spinal magnetic resonance imaging (MRI) studies at regular intervals to determine local control (LC). Pain and other symptom data were collected to determine treatment response and toxicity. Toxicity was graded using the Common Terminology Criteria for Adverse Events version 2.0 (CTCAE v2) guidelines and the McCormick neurologic function score. Survival outcomes were calculated using the Kaplan-Meier method, with factors affecting survival determined by log-rank test.

Results: Sixty-two patients with 67 tumors were treated with SBRT on protocol between 2002 and 2010. All patients underwent SBRT after spine surgery, which included laminectomy, corpectomy, vertebroplasty, or a combination of these techniques. The median tumor volume was 44.9 cm³ (range: 1.6–358 cm³), with renal cell carcinoma as the most common histology represented (48%). Forty patients (65%) were treated with prior radiation to the spine utilizing conventional fractionation (median dose 31.75 Gy). With a median follow-up of 19 months (range: 1–91 mo), the 1-year imaging LC was 82%, and overall survival (OS) was 71% (median: 25 months). Durable pain control, defined as a score of < 4 of 10 at 6 months, was achieved in 78% of patients. There was no difference in LC between patients treated with different surgical techniques (P = .47) or between radiation-naive patients versus those with prior treatment (P = .17). Tumor histology did not significantly correlate with the median time to progression (P = .35) or with OS (P = .30). Pain control at 1 month and 6 months after treatment was significantly correlated with improved LC (P < .01). There was a trend toward improved PFS for tumors below the level of the spinal cord, although this was not statistically significant (P = .09). Grade 3 toxicities included pain (four cases), dysphagia (one case), and nausea/vomiting/diarrhea (one case). One patient experienced a grade 4 neurologic toxicity, although this did not correlate with the treatment site.

Conclusion: This study represents the largest series of prospective data available on patients treated with SBRT in the postoperative setting. The combination of surgery with SBRT can offer patients with metastatic disease to the spine the chance of effective palliation, along with durable tumor control.

Proceedings of the 96th Annual Meeting of the American Radium Society - americanradiumsociety.org