Striking the Balance: Tailored Stereotactic Body Radiation Therapy for Osseous Spinal Metastases and Outcome Prediction
Menée à l'aide de données portant sur 121 patients présentant des métastases rachidiennes, cette étude détermine les conditions optimales de contourage du volume cible d'une radiothérapie stéréotaxique corporelle
Objective: Stereotactic body radiation therapy (SBRT) is increasingly used for spinal metastases (SM). Contouring for SBRT typically follows the International Spine Radiosurgery Consortium (ISRC) guidelines, leading to large planning target volumes (PTV). We compared minimal-volume contouring, which yields a more focused PTV, with conventional contouring and developed predictive models for adverse outcomes.
Methods: We analyzed all patients treated for SM at our center over the past decade. After exploratory and correlation analyses, we compared the contouring methods for adverse outcomes and PTV and spinal-cord (SC) dose distributions. Logit and support-vector-machine (SVM) models were used for outcome prediction.
Results: Among 121 patients (235 lesions), 147 lesions received minimal-volume contouring, 67 followed ISRC recommendations, and 21 were unassigned. The median prescription dose was 20 Gy (15–22 Gy) for single-session, and 24 Gy (19.5–30 Gy) for hypofractionated treatments. The median PTV was 11.1 ccm (0.2–173.7 ccm). Complications correlated significantly with pre-SBRT Karnofsky status (Cramer-V=0.277). Local control rates were comparable (80.5% vs. 78.4%), but complication rates were lower with minimal contouring (15.1% vs. 27.8%). Minimal contouring resulted in significantly higher median PTV BED (75.9 Gy vs. 57.5 Gy) and lower maximum SC BED (72.7 Gy vs. 81.9 Gy, both p<0.001). Logit models identified mean PTV (p=0.001) and vertebral dose (p<0.001) as significant predictors of vertebral fractures but showed limited accuracy (49.3% for local recurrence, 73.3% for fractures). SVM classifiers outperformed logit models, achieving higher accuracy (89.9% for recurrence, 92.0% for fractures) and improved PPVs (83.7% and 86.7%, respectively).
Conclusion: Minimal-volume target delineation based on thin-layer MRI and PSMA/FDG-PET-CT/MRI may be as effective as contouring according to the ISRC guidelines, if those imaging modalities are available. Further studies are warranted to assess minimal and expanded volumes. SVM models show promising potential for predicting patient outcomes, warranting further exploration.
Practical Radiation Oncology , article en libre accès, 2025