Keywords:
Oncology, Cone beam CT, Dosimetry, Cancer
Authors:
N. Mitina, T. Peterson, R. Guidi, C. Hargrave
DOI:
10.26044/ranzcr2023/C-285
Methods and materials
A systematic literature review was conducted on the PubMed MEDLINE database search to assess current published CI and GI values for spine metastases treated with SBRT.
Collection of data included a retrospective analysis of 49 SBRT treatment plans for patients treated for spine metastases at ROPART from April 2016 until March 2023. Human research ethics committee (EC00167) classified the project as exempt from ethical approval.
The following data was collected:
- CI and GI for all plans were calculated using equations seen in Figure 1 and 2 [1] for PTV and PTV Optimised (PTV excluding the thecal sac and spinal cord planning risk volumes) by Pinnacle3 (Philips Healthcare, Fitchburg, WI), treatment planning system script and also manually calculated. This was performed independently by two radiation therapists.
- Location of PTV (Cervical, Thoracic or Lumbar spinal levels)
- Number of involved vertebrae
- Volume of PTV in cubic centimentres (cc)
- Volume of overlap of PTV and PTV Optimised (PTV OPT) with critcal structures – spinal cord, thecal sac, nerve roots, cauda equina.
- PTV location in terms of segments of the vertebrae as shown in Figure 3
- Complexity rating of PTV in terms of number of segments (examples seen in figure 4). For the purpose of this study, in order to classify CTVs/PTVs by level of complexity, we separated PTV volumes into three catagories; LOW, MEDIUM and HIGH. These groups were based on the number of segments of the involved spine as defined by the International Spine Radiosurgery Consortium (ISRC) bony anatomic classification [6]. Complexity of the volume in this study refers to the degree to which the volume wraps around the spinal cord or cauda equina. Therefore volumes including 1-3 segments are classified as LOW, 4 segments classified at MEDIUM and 5-6 segments were claissified as HIGH.