Between the study years, 263 patients underwent spinal decompression and fusion, for which 148 patients met predetermined inclusion criteria. After 2:1 case-controlled matching, 99 were treated with CFR-PEEK instrumentation and 49 were treated with titanium instrumentation.

Demographic data for the two groups is reported in Table 1. Median age (p = 0.47) and sex (p = 0.343) were not significantly different between groups. The incidence of previous spine surgery and radiotherapy between groups did not differ (p = 0.236 and p = 0.829, respectively). There was no significant difference in the distribution of smoking status between groups at time of initial surgery, nor in number the pack-years in the patients who either currently smoked or had a history of smoking. The median follow-up time was significantly longer for the titanium group compared to CFR-PEEK (236 days versus 122.5 days, p < 0.0005). The overall top three primary malignancies between all patients were renal (n = 20), prostate (n = 19), and poorly differentiated carcinoma (n = 14).

Table 2 compares surgical characteristics and postoperative course, as well as oncologic outcomes between groups. The median number of index levels was 1 and 3 for CFR-PEEK and titanium, respectively (p < 0.001), and the length of construct spanned 5 levels for CFR-PEEK and 6 levels for titanium, respectively (p < 0.001). Patients who received CFR-PEEK instrumentation also had shorter operative time (p < 0.001), shorter hospital length of stay (p < 0.001) and decreased estimated blood loss (p < 0.001).

Table 3 describes adjuvant therapies administered to patients, as well as data evaluating functional status both pre- and post-operatively via ECOG scores. The percentage of patients receiving pre-operative systemic therapy was 32.3% for the CFR-PEEK group compared to 61.2% for the titanium group (p < 0.0005). Post operative systemic therapy was administered to 77.8% of CFR-PEEK patients compared to 46.9% of titanium patients (p < 0.0005). Utilization of PORT was similar between the two groups at 59.6% and 55.1% for CFR-PEEK and titanium (p = 0.6) respectively. Within the groups, PORT was performed with SBRT for 45 (76.3%) CFR-PEEK patients, and 15 (55.6%) titanium patients (p = 0.08). Of those treated with SBRT, the median prescription dose was 27 Gy for both CFR-PEEK and titanium (p = 0.91). There was no difference in the percent of patients with a pre-operative ECOG score of 0 and 1 between cohorts at 53% and 49% for CFR-PEEK and titanium, respectively (p = 0.73), as well as no significant difference in the percent of patients with a post-operative ECOG score of 0 and 1 at 32% for CFR-PEEK and 30.6% of titanium patients (p = 0.99).

Table 4 describes data related to post operative complications and patient outcomes. There was no significant difference in any of the measured post operative complications, including hardware failure, infection, or reoperation for tumor recurrence. The CFR-PEEK cohort had one patient with post-operative hardware failure requiring subsequent extension of the fusion construct and the titanium group had none (p = 0.5511). The CFR-PEEK cohort had two patients with post operative infections and the titanium group had one. In terms of reoperation for tumor recurrence at the index level, the CFR-PEEK cohort had 3 patients and the titanium group had 1. The CFR-PEEK cohort had 11 patients with post operative complications unrelated to spine surgery as listed in Table 4 and the titanium group had 5. Complications in the “other” category included pulmonary embolism, pneumonia, pleural effusion, acute kidney injury, decubitus ulcers, urosepsis, new onset eye dysfunction, hematuria, and deep vein thrombosis.

With respect to OS, the CFR-PEEK group had yet to reach the median OS compared to a median OS of 8.5 months in the titanium cohort (Fig. 1, p-value = 0.011). There was no significant difference in the incidence of local recurrence observed between the two groups at 22 (22.2%) for CFR-PEEK and 15 (30.6%) for titanium (p = 0.31). The PFS for all patients in the cohort was 143 days for the CFR-PEEK group and 214 days for the titanium group, respectively (p = 0.409, Fig. 2A). Among the patients that demonstrated recurrence, the recurrence was detected sooner in the CFR-PEEK group compared to the titanium group (94 days versus 189 days, respectively; p = 0.0013; Fig. 2B).

Kaplan-Meier curve representing the overall survival (OS) of patients with CFR-PEEK (red) and Titanium (blue) instrumentation. Censored patients represent patients alive at that time point but were either lost to follow up, or that time point was their most recent follow up based on surgical date

Kaplan-Meier curves representing the progression-free survival (PFS) of patients with CFR-PEEK (red) and Titanium (blue) instrumentation. (a) is the curves representing all patients from both cohorts (b) is the sub analysis curves for only patients in which recurrence/progression was noted at the index level, in each cohort. Censored patients represent patients alive at that time point but were either lost to follow up, or that time point was their most recent follow up based on surgical date

Figure 3 depicts the detection of tumor recurrence in one CFR-PEEK instrumented patient, and one titanium instrumented patient to highlight the differences in visualization of surrounding structures with the two materials.

Images of local recurrence detection in patients with CFR-PEEK instrumentation (a-c), and Titanium instrumentation (d-f)