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Commentary in response to ‘Preoperative tumor embolization prolongs time to recurrence of meningiomas: a retrospective propensity-matched analysis’

We read the study ‘Preoperative tumor embolization prolongs time to recurrence of meningiomas: a retrospective propensitymatched analysis’ by Akimoto et al with great interest. In this study, the authors study propensitymatched retrospective cohorts of 42 patients each to determine the impact of preoperative embolization on outcomes after resection of WHO grade 1 meningioma. All patients underwent preoperative catheterbased angiography. The authors found that embolization reduced blood loss and operative time, but did not improve gross total resection (GTR) rates. Recurrencefree survival (RFS) is 49 months for the embolized group and 24 months for the nonembolized group, a statistically significant finding, though the overall incidence of recurrence at followup is nonsignificant. We believe this study’s generalizability is limited by the outcomes presented and statistical methods used in this study. Additionally, we share reservations about such high utilization of preoperative embolization. The 5year recurrence rate within the 84patient cohort is 17%, stratified to approximately 10% after GTR (including Simpson grade 1–3 resection) and 50% after subtotal resection (STR). In recent studies of WHO grade 1 meningiomas, the 5year rate of recurrence after GTR is reported to be 5–10% and 20–30% after STR. Within Simpson 1 or Simpson ‘zero’ resection, recurrence for many grade 1 meningiomas should be nearly nonexistent. 6 The rates of recurrence in this study appear higher than prior studies, especially after STR, even compared with those that do not use embolization. Preoperative embolization also did not affect recurrence or time to recurrence in a similar study of grade 1 meningioma with an overall recurrence rate of 11% (table 4 in Haddad et al). Certain reports have recurrence rates closer in line with this study, which suggests differences in patient populations, surgical technique, pathologic interpretation, radiographic interpretation, or followup patterns. 8 We also note that this study may not be adequately powered to conclude that preoperative embolization does not increase neurologic complications. A study with 1:1 enrollment powered at an alpha of 0.05 and beta of 0.2 to find a 10% difference in the incidence of a dichotomous variable such as complication rate would require nearly double this cohort size at a minimum. This study is powered to identify a change in incidence of 16% at the highest, which is relevant when considering the 9% increase in overall complication rate for embolized patients compared with nonembolized patients as well. Preoperative embolization for meningioma is associated with a 1–9% risk of neurologic morbidity, in line with the reported value of 7% in this study. The benefits of embolization should outweigh additive risk of neurologic morbidity from preoperative embolization, but some of these benefits remain controversial. In our institution, we use dynamic computed tomography angiography for routine preoperative vascular imaging for most meningiomas to negate the periprocedural risk of catheterbased angiography. We have described the imaging protocol previously. We have performed approximately 100 meningioma resections between July 29, 2021 and July 14, 2022, and of these we employed diagnostic angiography in two cases and embolization in no cases (unpublished data). We find that in the majority of our cases, hemostasis for these vascular tumors can be managed well with early devascularization without preoperative embolization, thus eliminating the additive risk of neurologic morbidity from angiography and intervention. Reducing the dural vascular supply feeding a meningioma may arrest the progression of residual disease. It would be helpful to know whether the longterm benefit of embolization on RFS differed based on extent of resection. It would additionally be helpful to know which meningiomas were embolized in this study and why the propensitymatching in this study does not take into account surgically relevant anatomic details like the location and size of feeding arteries, number of arteries embolized, the presence of pial invasion, and venous drainage patterns. At this time it remains unclear to us whether preoperative embolization improves RFS rates for meningioma surgery. The clinical outcomes reported (including a relatively high recurrence rate) and lack of statistical sensitivity for complications reduces the generalizability and questions the conclusion that preoperative embolization may reduce time to recurrence without increasing neurologic morbidity. We commend the authors for a unique contribution in studying the effect of preoperative embolization on longterm disease control. Multicenter studies and standardization of reporting guidelines may help reduce this heterogeneity.