Do patient-specific cutting guides for pelvic and sacral tumour resection provide tumour-free bone margins?

Background: Achieving R0 margin, i.e., tumour-free margin, during conservative surgery for pelvic or sacral tumours is demanding. Small cohort studies suggest that patient-specific instrumentation (PSI) may hold promise, notably for bone margin accuracy. Objectives of this study were to determine whether PSI allowed R0 bone margins; R0 soft-tissue margins; and increased disease-free survival, without local recurrence or distant metastases, comparatively to previous studies of patients treated by free-hand or navigated surgery; and whether PSI positioning for the bone cuts was readily achieved.

Hypothesis: Using PSI provides R0 bone margins in 100% patients and improves disease-free survival).

Material and methods: Retrospective study including consecutively patients who underwent PSI-assisted surgical resection of a pelvic or sacral tumour between October 2011 and February 2020. Bone and soft-tissue margins were assessed according to the Union for International Cancer Control classification. Overall survival and disease-free survival were evaluated using the Kaplan-Meier method. PSI positioning was assessed by surgeons for each patient on a scale from 5 (excellent) to 1 (failed).

Results: Of the 42 included patients (26 males and 16 females), 34 had primary bone malignancies, 3 had soft-tissue malignancies extended to the bone, 3 had locally aggressive benign bone tumours, and 2 had solitary bone metastases. Mean follow-up was 49 (range 4-112) mo. Bone margins were as follow: R0 in 40 (95%) patients; R1 in 1 (2.5%) and R2 in 1 (2.5%). Soft-tissue margins were as follow: R0 in 76% of patients; R1 in 21.5% of patients. At 5 years, overall disease-free survival was 63.4% (95% CI, 49.3-81.4), survival without local recurrence was 65.5% (95% CI, 47.7-90.0], and survival without distant metastases was 70.1% (95% CI, 55.4-88.5). Positioning of the 60 PSIs used was rated excellent or good in 93.3% of cases and fair or poor in 6.7% of cases; no cases of positioning failure were recorded.

Discussion: PSIs provided excellent accuracy for achieving R0 bone margin. Nonetheless, local recurrence remained high similarly to free-hand surgery. This finding may be related to surgeons relying on PSI's accuracy for maximal preservation.

Conclusion: PSIs are technically reliable and safe for obtaining R0 margins during conservative resection surgery to treat pelvic and sacral tumours. However, PSIs do not substantially decrease the local recurrence rate.

Level of evidence: IV; retrospective observational cohort study.