Introduction: Preoperative Onyx embolization of cranial and spinal tumors is safe and effective; however, current measures of procedural success may not reflect surgical outcomes. Our objective was to compare angiographic and histologic Onyx penetration and further assess its efficacy as a preoperative embolic agent for neoplasms of the head, neck, and spine.
Methods: We retrospectively analyzed cases of preoperative Onyx embolization for treatment of head, neck, and spine tumors from 2009-2011. Patient demographics, as well as characteristics of the embolization procedure and surgical resection were recorded. Measures of Onyx efficacy included intraoperative blood loss and length of surgery. Angiographic and histologic penetration, as well as percent tumor devascularization, were assessed as predictors of efficacy using nonparametric hypothesis testing and linear regression.
Results: Of 22 patients (age range 3-77 years), 17 underwent preoperative Onyx embolization for head or neck pathology and 5 for spinal lesions. Good angiographic penetration was reported in 41% of tumors and central histologic penetration in 59%, with mean tumor devascularization of 85.3% (SD 12.6%); no correlation was identified. Mean surgical blood loss was 1342 mL (SD 1327 mL) and length of surgery was 289 minutes (SD 162 minutes). Neither angiographic, nor histologic Onyx penetration predicted blood loss (p=0.38, p=0.32 respectively) or surgical length (p=0.62, 0.90, respectively). Devascularization was not associated with blood loss (p=0.62), but it was a negative predictor of surgical length (p=0.013).
Conclusions: Preoperative Onyx embolization of head, neck, and spine tumors is capable of achieving deep tumor penetration, as identified on postoperative histology, even when not visualized on angiography. We did not identify an association between these measures of embolization adequacy, suggesting that there may be limited utility in using angiographic devascularization as the ultimate arbiter of procedural success.
Patient Care: Currently, the success of preoperative tumor embolization is determined by demonstration of tumor devascularization. If devascularization requires obliteration of the intralesional capillary bed and proximal feeding vessels, comparing pre- and post-embolization tumor blush on angiography should serve as an accurate gauge of success. However, if angiographic devascularization does not correlate with the intended purpose of preoperative embolization, i.e. to decrease surgical blood loss and operative time, it may not be an appropriate arbiter of procedural success. By identifying the feasibility of microscopic Onyx penetration into the center of the tumor via postoperative pathology analysis, as well as cases of mismatch between angiographic and histologic penetrance, our study suggests that visualized angiographic penetrance may not be necessary to achieve the goals of preoperative embolization.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Discuss, in small groups, measures of successful preoperative tumor embolizations.
2) Discuss, in small groups, the relationship between degree of tumor penetration by the embolic agent and surgical outcomes, such as blood loss and length of surgery.