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Toxicity Analysis and Outcomes for Lumbar and Sacral Spinal Tumors Treated with Stereotactic Body Radiotherapy

2011; Elsevier BV; Volume: 81; Issue: 2 Linguagem: Inglês

10.1016/j.ijrobp.2011.06.1911

1879-355X

Samuel T. Chao, Ehsan H. Balagamwala, T. Djemil, Ovidiu Marina, C.A. Reddy, John H. Suh, Ping Xia, Lilyana Angelov,

Spine and Intervertebral Disc Pathology

Stereotactic body radiotherapy (SBRT) is an effective treatment option for spinal tumors. The tolerance of the cauda equina (CE) may be greater than that of the spinal cord. For patients treated near the CE, we studied the correlation between CE dosimetry and neurological toxicity (NTox), and renal dosimetry and toxicity (RTox). Patients with spinal tumors treated at L2 or below were eligible. Of 83 treatments (70 patients), 77 treatments (tx) with ≥1 mo follow-up were included. NTox was scored based on CTCAEv4.0 criteria and RTox was defined as >50% rise in creatinine post-SBRT. Radiographic failure was defined as in-field or adjacent (within 1 vertebral body) failure on MRI. Pain relief was based on the Brief Pain Inventory and adjusted for narcotic use per RTOG 0631. Dosimetric endpoints of the CE included maximum dose (MD), D0.035, D0.1, D1, V8, V10, V12, V14, V16, and conformality (CI) and heterogeneity indices. Dosimetric endpoints of the kidney included V4, V6, V8 and V10. Complete dosimetry was available for 58 tx. Logistic regression, Kaplan-Meier and Cox proportional hazards modeling were utilized for statistical analysis. Median age, follow-up, and median survival were 60 yr (range, 27 - 87 yr), 8.3 mo (1 - 38 mo) and 11.7 mo, respectively. Median SBRT dose was 15 Gy (10 - 24 Gy) in 1 fx (1 - 5 fx). No Grade 3 or 4 toxicity was observed. Ten patients developed NTox: Grade 1 sensory (n = 8), Grade 2 sensory (n = 1), Grade 1 motor (n = 2), Grade 2 motor (n = 2). V10 >10% and V12 >10% was found in 20% and 2% patients, respectively. CE dosimetry was not correlated with the development of NTox (p>0.05), however, the CI approached significance (OR: 29.6, p = 0.075). Four patients developed RTox. Median renal V8 was 0% (0 - 18.7%); renal dosimetry was not correlated with the development of RTox (p>0.05), suggesting elevation in creatinine is multifactorial. The majority of patients (73%) had improvement in pain post-SBRT; the median actuarial time to pain relief was 1.3 mo. Median actuarial time to symptomatic and radiographic failure was 26.8 and 28.6 mo, respectively. The symptomatic and radiographic progression-free survival at 6/12 mo was 83%/68% and 90%/73%, respectively. No clinical variables were correlated with radiographic failure. Dose ≤14 Gy (HR 4.6, p = 0.004), paraspinal disease (HR 3.0, p = 0.02) and uncontrolled systemic disease (HR 4.2, p = 0.01) were correlated with symptomatic failure. SBRT for lumbosacral tumors offers fast, durable pain relief that lasts beyond the expected survival of patients with metastatic disease. Using higher CE planning dose constraints (V12 ≤10% and MD ≤16 Gy) seems justified given the acceptable level of toxicity as demonstrated in this study. More data is needed to establish renal dose constraints.