(I-505) A combined hybrid surgery with reduced field irradiated volume approach does not increase adjacent level progression in metastatic spine patients
Resident University of Michigan Ann Arbor, Michigan, United States
Introduction: As the life span of cancer patients increases, so does the prevalence of metastases, especially to the spine. Most patients with spinal metastases will develop additional metastases during their treatment. In the past, the radiation Planned Targeted Volume of treatment (PTV) involved the tumor volume plus a half a vertebral level above and below. To minimize the adjacent level dose, we have reduced the PTV to the actual Gross Tumor Volume (GTV) on MRI. A reduced PTV has been shown to decrease the risk of radiation effect to adjacent vertebral bodies including risk of fractures. The purpose of this study was to examine if piecemeal separation surgery increased the risk of tumor spread in conjunction with our minimal PTV by examining adjacent level disease progression.
Methods: We performed a retrospective analysis of a prospectively maintained database of adult spinal oncologic patients who underwent stereotactic body radiotherapy (SBRT) to the spine at University of Michigan from 2010 to 2021.
Results: Four hundred and ninety-eight radiographic isocenters were identified in 417 patients. Of these, 366 (73.5%) isocenters were treated with SBRT, while 132 (26.5%) isocenters were treated with SBRT+surg. Patients treated with SBRT were significantly older (63.3yrs) compared to the SBRT+surg group (60.2 yrs; p=0.02). All other social economic factors including body mass index, marital status, insurance type, and having a primary care physician were similar between groups. More radiosensitive histologies were treated with SBRT (34%) compared to 11% for the SBRT+surg group. As expected, lesions treated in the SBRT+surg group had significantly more severe compression (65%) compared to the SBRT group (8%) (p < 0.001). The adjacent level progression was not significantly different between the groups (20.5% vs 22.1%; p=0.39). Furthermore, death between SBRT and SBRT+surg were similar (56.6% vs 65.9%; p=0.06).
Conclusion : Spine oncology patients treated with SBRT+surg have similar adjacent level progression compared to SBRT alone, suggesting the piecemeal separation surgery approach does not increase the risk of adjacent level disease when combined with reduced PTV radiation therapy.
