Abstract
BACKGROUND: Oligometastatic disease (5 metastases) is considered an intermediate cancer state of limited metastatic capacity and improved prognosis. Hence, in recent years, treatment of oligometastatic spinal disease has trended towards more definitive, ablative therapies. Little is known about the actual prognosis of patients presenting with oligometastatic spinal disease. The focus of this study was to compare oligometastatic spine patients to those with polymetastatic disease (>5 metastases). METHODS: This is an international, multicenter analysis of prospectively collected data. Data collected included demographics, survival, local control, histology, number and location of spine metastases, epidural spine cord compression (ESCC), the Spinal Instability Neoplastic Score (SINS), systemic disease burden, and treatment details. Health-related quality of life (HrQOL) measures included; numeric rating scale (NRS) for pain, EuroQol-5D (EQ-5D-3L), short form 36 version 2 (SF-36v2) and the spine oncology study group outcomes questionnaire (SOSGOQ). RESULTS: A total of 393 patients were included, of which 215 presented with oligometastatic disease and 178 with polymetastatic disease. A significant survival advantage was found for patients presenting with oligometastatic disease compared to those with polymetastatic disease at time of initial treatment of spinal metastases. This survival advantage was noticeable in both operative and non-operative patients. Local control rates were higher in the oligometastatic group for the spinal level treated. Furthermore, both groups experienced significant improvement in multiple HrQOL measures at 6 months post-treatment with no differences in these outcome measures between the two groups. CONCLUSION: At time of treatment of spinal metastatic disease, oligometastatic disease offers a significant survival advantage compared to polymetastatic disease, regardless of treatment choice. Local control can be achieved in both groups. HrQOL measures improve in both groups post-treatment, thus demonstrating a palliative treatment benefit for all treated patients. Our results support the oligometastatic theory and the current trend of ablative treatment for oligometastatic spine disease.