Peripheral nervous system injury after high-dose single-fraction image-guided stereotactic radiosurgery for spine tumors.

OBJECTIVE The object of this study was to determine the percentage of high-dose (1800-2600 cGy) single-fraction stereotactic radiosurgery (SF-SRS) treatments to the spine that result in peripheral nervous system (PNS) injury. METHODS All patients treated with SF-SRS for primary or metastatic spine tumors between January 2004 and May 2013 and referred to the Rehabilitation Medicine Service for evaluation and treatment of neuromuscular, musculoskeletal, or functional impairments or pain were retrospectively identified. RESULTS Five hundred fifty-seven SF-SRS treatments in 447 patients resulted in 14 PNS injuries in 13 patients. All injures resulted from SF-SRS delivered to the cervical or lumbosacral spine at 2400 cGy. The overall percentage of SF-SRS treatments resulting in PNS injury was 2.5%, increasing to 4.5% when the thoracic spine was excluded from analysis. The median time to symptom onset following SF-SRS was 10 months (range 4-32 months). The plexus (cervical, brachial, and/or lumbosacral) was affected clinically and/or electrophysiologically in 12 (86%) of 14 cases, the nerve root in 2 (14%) of 14, and both in 6 (43%) of 14 cases. All patients experienced pain and most (93%) developed weakness. Peripheral nervous system injuries were CTCAE Grade 1 in 14% of cases, 2 in 64%, and 3 in 21%. No dose relationship between SF-SRS dose and PNS injury was detected. CONCLUSIONS Single-fraction SRS to the spine can result in PNS injury with major implications for function and quality of life.

Prognostic factors for spinal chordomas and chondrosarcomas treated with postoperative pencil-beam scanning proton therapy: a large, single-institution experience.

OBJECTIVE: The aim of this paper was to evaluate the prognostic factors in surgical and adjuvant care for spinal chordomas and chondrosarcomas after surgery followed by high-dose pencil-beam scanning proton therapy (PBS-PT). METHODS: From 1997 to 2016, 155 patients (61 female patients; median age 55 years) with spinal (cervical, n = 61; thoracic, n = 29; lumbar, n = 13; sacral, n = 46; pelvic, n = 6) classic chordomas (n = 116) and chondrosarcomas (n = 39; most were low grade) were treated with maximal safe resection followed by PBS-PT (median dose prescribed: 74 Gy [relative biological effectiveness], range 48.6-77 Gy). The majority of patients (n = 153, 98.7%) had undergone at least 1 resection prior to PBS-PT (median 1, range 0-5; biopsy only, n = 2). Fewer than half (45.1%) of the surgeries were rated as gross-total resections (GTRs) prior to PBS-PT. Surgical stabilization (SS) was present in 39% of all patients (n = 60). Ninety-one patients (59%) presented with macroscopic tumor at the start of PBS-PT. The median follow-up duration was 64.7 months (range 12.2-204.8 months). RESULTS: The 5-year local tumor control, disease-free survival (DFS), and overall survival were 64.9% (95% CI 56.3%-73.5%), 59.4% (95% CI 50.6%-68.2%), and 77.9% (95% CI 70.6%-85.2%), respectively. In total, 63 patients (40.6%) experienced failure during the follow-up period: local only in 32 (20.6%), distal only in 7 (4.5%), local + distal in 19 (12.3%), surgical pathway failure (SPF) only in 2 (1.3%), local + SPF in 2 (1.3%), and distal + SPF in 1 (< 1%). Univariate analysis identified gross residual disease, the presence of SS, and treatment era prior to 2008 as highly significant for worse outcome, with all 3 remaining significant on multivariate analysis. The type of surgery (GTR or subtotal resection/biopsy) and whether GTR was achieved by en bloc or curettage did not show a significant prognostic effect. Surgical complications prior to PBS-PT were present in 42.5% of all surgically treated patients and were seen more commonly in patients with multiple surgical interventions (p = 0.005) and those operated on with the intent of en bloc resection (p = 0.006). CONCLUSIONS: The extent of resection and metallic stabilization substantially influenced clinical outcomes for patients with spinal chordoma or chondrosarcoma despite high-dose adjuvant PBS-PT. Optimal upfront surgical management of these tumors continues to include GTR, as possible, with prompt adjuvant proton therapy.

The impact of decompression with instrumentation on local failure following spine stereotactic radiosurgery.

OBJECTIVE Spine stereotactic radiosurgery (SRS) is a safe and effective treatment for spinal metastases. However, it is unknown whether this highly conformal radiation technique is suitable at instrumented sites given the potential for microscopic disease seeding. The authors hypothesized that spinal decompression with instrumentation is not associated with increased local failure (LF) following SRS. METHODS A 2:1 propensity-matched retrospective cohort study of patients undergoing SRS for spinal metastasis was conducted. Patients with less than 1 month of radiographic follow-up were excluded. Each SRS treatment with spinal decompression and instrumentation was propensity matched to 2 controls without decompression or instrumentation on the basis of demographic, disease-related, dosimetric, and treatment-site characteristics. Standardized differences were used to assess for balance between matched cohorts. The primary outcome was the 12-month cumulative incidence of LF, with death as a competing risk. Lesions demonstrating any in-field progression were considered LFs. Secondary outcomes of interest were post-SRS pain flare, vertebral compression fracture, instrumentation failure, and any Grade ≥ 3 toxicity. Cumulative incidences analysis was used to estimate LF in each cohort, which were compared via Gray's test. Multivariate competing-risks regression was then used to adjust for prespecified covariates. RESULTS Of 650 candidates for the control group, 166 were propensity matched to 83 patients with instrumentation. Baseline characteristics were well balanced. The median prescription dose was 16 Gy in each cohort. The 12-month cumulative incidence of LF was not statistically significantly different between cohorts (22.8% [instrumentation] vs 15.8% [control], p = 0.25). After adjusting for the prespecified covariates in a multivariate competing-risks model, decompression with instrumentation did not contribute to a greater risk of LF (HR 1.21, 95% CI 0.74-1.98, p = 0.45). The incidences of post-SRS pain flare (11% vs 14%, p = 0.55), vertebral compression fracture (12% vs 22%, p = 0.04), and Grade ≥ 3 toxicity (1% vs 1%, p = 1.00) were not increased at instrumented sites. No instrumentation failures were observed. CONCLUSIONS In this propensity-matched analysis, LF and toxicity were similar among cohorts, suggesting that decompression with instrumentation does not significantly impact the efficacy or safety of spine SRS. Accordingly, spinal instrumentation may not be a contraindication to SRS. Future studies comparing SRS to conventional radiotherapy at instrumented sites in matched populations are warranted.

Spine stereotactic radiosurgery for metastatic sarcoma: patterns of failure and radiation treatment volume considerations.

OBJECTIVE Given the relatively lower radiosensitivity of sarcomas and the locally infiltrative patterns of spread, the authors sought to investigate spine stereotactic radiosurgery (SSRS) outcomes for metastatic sarcomas and to analyze patterns of failure. METHODS The records of 48 patients with 66 sarcoma spinal metastases consecutively treated with SSRS between 2002 and 2013 were reviewed. The Kaplan-Meier method was used to estimate rates of overall survival (OS) and local control (LC). Local recurrences were categorized as occurring infield (within the 95% isodose line [IDL]), marginally (between the 20% and 95% IDLs), or out of field. RESULTS Median follow-up time was 19 months (range 1-121 months), and median age was 53 years (range 17-85 years). The most commonly treated histology was leiomyosarcoma (42%). Approximately two-thirds of the patients were treated with definitive SSRS (44 [67%]) versus postoperatively (22 [33%]). The actuarial 1-year OS and LC rates were 67% and 81%, respectively. Eighteen patients had a local relapse, which was more significantly associated with postoperative SSRS (p = 0.04). On multivariate modeling, receipt of postoperative SSRS neared significance for poorer LC (p = 0.06, subhazard ratio [SHR] 2.33), while only 2 covariates emerged as significantly correlated with LC: 1) biological equivalent dose (BED) > 48 Gy (vs BED ≤ 48 Gy, p = 0.006, SHR 0.21) and 2) single vertebral body involvement (vs multiple bodies, p = 0.03, SHR 0.27). Of the 18 local recurrences, 14 (78%) occurred at the margin, and while the majority of these cases relapsed within the epidural space, 4 relapsed within the paraspinal soft tissue. In addition, 1 relapse occurred out of field. Finally, the most common acute toxicity was fatigue (15 cases), with few late toxicities (4 insufficiency fractures, 3 neuropathies). CONCLUSIONS For metastatic sarcomas, SSRS provides durable tumor control with minimal toxicity. High-dose single-fraction regimens offer optimal LC, and given the infiltrative nature of sarcomas, when paraspinal soft tissues are involved, larger treatment volumes may be warranted.