Evaluation of a Dedicated Software Elements T Spine SRS, Brainlab® for Target Volume Definition in the Treatment of Spinal Bone Metastases With Stereotactic Body Radiotherapy

Introduction: Stereotactic body radiotherapy (SBRT) is a treatment option for spine metastases. The International Spine Radiosurgery Consortium (ISRC) has published consensus guidelines for target delineation in spine SBRT. A new software called ElementsT Spine SRS by Brainlab (R) that includes the module Elements SmartBrush Spine (v3.0, Munich, Germany) has been developed specifically for SBRT treatment of spine metastases, and the latter provides the ability to perform semiautomatic clinical target volume (CTV) generation based on gross tumor volume (GTV) localization and guidelines. The aims of our study were to evaluate this software by studying differences in volumes between semiautomatic CTV contours compared to manual contouring performed by an expert radiation oncologist and to determine the dosimetric impact of these differences on treatment plans. Methods: A total of 35 volumes (Expert GTV and Expert CTV) from 30 patients were defined by a single expert. A semiautomatic definition of these 35 CTVs based on the location of Expert GTV and following ISRC guidelines was also performed in Elements SmartBrush Spine (Brainlab CTV). The spatial overlap between Brainlab and Expert CTVs was calculated using the Dice similarity coefficient (DSC). We considered a threshold of 0.80 or above to indicate that Elements SmartBrush Spine performed very well with adequate contours for clinical use. Two dosimetric treatment plans, each corresponding to a specific planning target volume (PTV; Expert PTV, Brainlab PTV), were created for 11 patients. Results: We showed that Brainlab CTV and Expert CTV mean volumes were 29.8 +/- 16.1 and 28.7 +/- 15.7 cm(3), respectively (p = 0.23). We also showed that the mean DSC for semiautomatic contouring relative to expert manual contouring was 0.85 +/- 0.08 and less than 0.80 in five cases. For metastases involving the vertebral body only (n = 13,37%), the mean DSC was 0.90 +/- 0.03, and for ones involving other or several vertebral regions (n = 22.63%), the mean DSC was 0.81 +/- 0.08 (p < 0.001). The comparison of dosimetric treatment plans was performed for equivalent PTV coverage. There were no differences between doses received by organs at risk (spinal cord and esophagus) for Expert and Brainlab PTVs, respectively. Conclusion: The results showed that the semiautomatic method had quite good accuracy and can be used in clinical routine even for complex lesions.

Automated summary

The study found that the Brainlab software provides accurate assessment of treatment plans for spine metastases, demonstrating high potential for versatile and reliable clinical applications.