(P 506) THE EFFECT OF TIMING BETWEEN PRE-OPERATIVE EMBOLIZATION AND SURGERY: A RETROSPECTIVE ANALYSIS OF HYPERVASCULAR BONE METASTASES

Objective: Pre-operative embolization for metastatic bone lesions has the potential to reduce intra-operative blood loss and improve perioperative outcomes in patients with hypervascular tumors. The optimal timing between embolization and surgery has yet to be established. Our analysis sought to evaluate how the timing of embolization ( < 24 hours vs. >24 hours) prior to surgery impacts blood loss, transfusion risk, and operative time in patients with hypervascular primary tumors.

Methods: We identified patients with renal cell (RCC) or thyroid carcinoma undergoing surgery between 1992 and 2023 (Table 1). These patients were segregated into the following cohorts: 1) no embolization pre-operatively, 2) surgery within 24 hours of embolization, and 3) surgery greater than 24 hours after embolization. Our primary outcomes were estimated blood loss (EBL), operative time, perioperative transfusion rate, and change in hemoglobin during the perioperative period. Multivariate logistic regression analyses were performed to assess the effect of pre-operative embolization and its timing while controlling for patient age, American Society of Anesthesiology (ASA) Class, lesion size, type of procedure, and the presence of a pathologic fracture. For EBL and operative time, patients were segregated into high or low categories based on median values. For perioperative hemoglobin changes, patients were similarly segregated based on mean values.

Results: No differences were seen in all evaluated outcomes between immediate and delayed embolization cohorts (Table 2). When comparing those with and without embolization, no differences were seen in EBL, transfusion rates, or hemoglobin changes (Table 3). Patients without embolization had a significantly lower operative time. No differences in EBL were seen between the immediate (OR: 0.685, 95% CI: 0.159-2.949; p=0.611) and delayed (OR: 0.568, 95% CI: 0.093-3.462; p=0.539) surgery cohorts compared to patients without embolization. Surgery greater than 24 hours after embolization was not associated with a higher risk of prolonged operative time (OR: 13.499, 95% CI: 0.832-219.146; p=0.067). No differences in transfusion incidence or hemoglobin drop were seen between embolization cohorts.

Conclusion: Surgery within 24 hours of embolization did not significantly reduce blood loss, transfusion rate, operative time, or hemoglobin change compared to surgery at later time interval. Similarly, no differences in these outcomes were seen between patients with and without embolization. These findings suggest that surgery may be safely delayed beyond 24 hours from embolization without a higher risk of bleeding. Similarly, in appropriately selected cohorts, embolization may not be needed pre-operatively. No larger study has evaluated embolization timing among patients with metastases in various anatomic regions. It remains important to consider how selection bias may influence choices regarding embolization and procedures performed.