Radical Surgical Treatment of Spinal Oligometastatic Disease with Metastatic Spinal Cord Compression–Outcome and Evaluation of Feasibility of Carbon Fibre Reinforced PEEK Instrumentation in Comparison to Standard Titanium Fixation
Authors: Saha Priyanshu , Siller Sebastian , Cox Kofi , Uthayanan Leshanth , Buckley Thomas , Tsang Emily , Hwang Zion , Ajayi Bisola , Kurban Tesfaldet , Ahmed Merina , Khoo Vincent , Bernard Jason , Bishop Timothy , Silva Vino , Minhas Pawan , Papadopoulos Marios , Lui Darren F. 
Published: February 2024

Introduction:
Oligometastatic disease (≤ 3 extracranial metastases) is hypothesised as the intermediary state between localised and widespread metastatic disease. However, in terms of spinal oligometastatic disease, data on oncological outcome after radical surgical treatment are still lacking in literature. The same applies to the advantages of CFR-PEEK instrumentation in this specific patient cohort compared to the use of titanium fixation.
Methods:
We retrospectively analysed our prospectively collected consecutive cohort of patients undergoing radical surgical treatment (en-bloc and separation surgery) for spinal oligometastatic disease between 2018–2023 at our quaternary level 1 spinal centre; whenever possible postoperative SBRT was applied post adjuvant alongside systemic oncological treatment. Patient demographics, surgical and oncological characteristics as well as outcomes with regards to hardware malfunction, local recurrence rates and mortality were investigated and compared between the group with CFR-PEEK (CF) instrumentation and a control group with standard titanium (Ti) fixation. Follow-up was at least 12 months in every patient which ranged up to 60 months.
Results:
A total of 25 oligometastatic MSCC patients (mean age 58.8, male: 51%) all with Bilsky Score 1c or greater) who underwent radical surgical treatment using CFR-PEEK fixation (en-bloc: 5 patients, separation surgery: 20) for varying tumour histologies were included and compared to 24 patients (en-bloc: 4 patients, separation surgery: 20) with standard Ti fixation. Mean operation time, intraoperative blood loss, and length of inpatient stay for Separation Surgery was 234.8 minutes, 726.7ml and 21.0 days without any statistical differences between both CF and Ti groups. Mean operation time, intraoperative blood loss and length of inpatient stay for En Bloc was 718.3 minutes, 2345.0 ml and 55.0 days without any statistical differences between both CF and Ti groups. Postoperative complication rate was 11% (no significant differences between the CFR-PEEK and Ti group). At the last interval scan (mean: 17 months post-operative), the rate of construct failure or screw breakage was 0% in both CFR-PEEK and Ti groups. 2 patients in the CFR-PEEK group and 3 patients of the Ti group did not receive postoperative adjuvant SBRT due to inpatient death, autonomy, and non-local recurrent disease. While overall 1-year survival and local tumour control rates were 90% (100% in Separation Surgery) and 100% respectively in patients who received adjuvant SBRT, it was markedly worse in those patients that did not receive adjuvant SBRT (50% vs 0%); there were no significant differences in oncological survival between the CFR-PEEK and Ti groups (p = 0.4299).
Conclusion:
Radical surgical treatment concepts plus adjuvant SBRT are feasible in spinal oligometastatic disease and enable a favourable prognosis. The use of CF instrumentation in this context is equally safe compared to standard titanium fixation and may be beneficial due to its material-inherent advantages allowing superior planning and delivery of radiotherapy and the reduced artefacts on postoperative imaging.