LAUSR

Surgery for skull base meningiomas is frequently limited to subtotal resection (Simpson grade IV) to preserve critical anatomical structures and neurological function. On the other hand, the relevance of a maximum resection for tumor progression is increasingly discussed. In this context, we recently demonstrated an increased risk of tumor progression after Simpson grade IV resection in skull base meningiomas, while prognosis was similar after grade I–III surgery [1]. However, “Simpson grade IV resection” as classified by the neurosurgeon is imprecise and the influence of the amount of meningioma remnants on progression, especially in skull base lesions, is largely unknown. We therefore investigated the impact of the postoperative tumor volume on progression in patients from the same series who underwent Simpson grade IV resections of primary diagnosed skull base meningiomas. The extent of resection according to the Simpson classification had been obtained from operative reports in each case. Data recovery and follow-up has been described previously [1]. For this study, tumor volume on initial postoperative imaging performed within 12 months after surgery was segmented using an established semi-automatic technique (Medical Imaging Toolkit; MITK, Istituto di Calcolo ad Alte Prestazioni, Napoli, Italy) by a radiologist blinded to any follow-up data (Fig. 1). Follow-up imaging was analyzed by a team of at least one neurosurgeon and one (neuro-)radiologist and progression was defined in case of any increase of tumor size greater than CT or MRI resolution capacity [1]. Associations between the postoperative tumor volumes and progression were then investigated in statistical analyses. Using this approach, eligible postoperative imaging and follow-up data of 49 of the 62 patients who underwent Simpson grade IV resection in our previous series [1] were available (79%). Clinical, histopathological and radiological data are summarized in Table 1. Surgery was performed between 2007 and 2015. Imaging was performed after a median of 3 months after surgery (range 0–12 months) and included contrast-enhanced magnet resonance imaging (MRI) in 45 individuals (92%) and, due to contraindications against MRI, computed tomography (CT) scans in 4 of 49 patients (8%), respectively. Median postoperative tumor volume was 2.99 cubic centimeter (ccm, range .02–67.08 ccm) and significantly varied among the different tumor locations. Hence, median tumor volume was .75, 9.36, 3.81 and 8.51 ccm in sphenoid ridge, cerebello pontine angle, petroclival/clival and foramen magnum meningiomas and .16 ccm in tumors of other skull base locations (p = .008, Kruskal–Wallis-H test). Duration of surgery positively correlated with postoperative tissue volume (p = .001, Pearson test). Postoperative tumor volume was independent of the use of intraoperative neuronavigation (p = .515) but was higher after surgeries in which neurophysiological monitoring was used (p = .009, Mann–Whitney-U test). Within a median follow-up period of 41 months (range 1–96 months), tumor progression was observed in 13 patients (27%) after a median progression free interval (PFI) of 24 months (range 4–50 months). During follow-up, 15 of 47 patients (32%) with available data received adjuvant radiation therapy prior to progression after a median of 9 months (range 3–96 month), while 32 individuals were followed-up without irradiation. Among those, preoperative irradiation had been performed in 2 individuals (4%). Thus, analyzes included 30 irradiation-naive patients until the date of progression. None of the patients had received irradiation prior to initial postoperative MRI. Median PFI was 14 months in atypical meningiomas but was not reached * Benjamin Brokinkel [email protected]