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MO_14_2809 - Is Risk Group-Adapted Adjuvant Radiation Therapy Beneficial for WHO Grade I/II Skull Base Meningioma? a Propensity Score-Matched Analysis

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Is Risk Group-Adapted Adjuvant Radiation Therapy Beneficial for WHO Grade I/II Skull Base Meningioma? a Propensity Score-Matched Analysis
S. Park1, Y. J. Cha2, S. H. Suh3, I. J. Lee4, K. S. Lee5, C. K. Hong5, and J. W. Kim4; 1Department of Radiation Oncology, Yonsei University College of Medicine, Seoul, Korea, Republic of (South), 2Department of Pathology, Yonsei University College of Medicine, Seoul, Korea, Republic of (South), 3Department of Radiology, Yonsei University College of Medicine, Seoul, Korea, Republic of (South), 4Department of Radiation Oncology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea, Republic of (South), 5Department of Neurosurgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea, Republic of (South)

Purpose/Objective(s): Reoperation for a recurrent meningioma in the skull base carries a substantial risk of complications. Prognostic factors associated with recurrence after initial surgery and the role of adjuvant radiotherapy (RT) for WHO grade I/II skull base meningioma are evaluated.

Materials/Methods: We reviewed 251 patients who underwent surgery for WHO grade I/II meningioma of the skull base between January 2000 and December 2016. Among these, 29 patients received adjuvant RT (RT group), while 222 patients did not (non-RT group). In the RT group, 20 patients received conventionally fractionated RT and 9 received gamma knife surgery (GKS). The median RT dose was 54.6 Gy (range, 49.4-60.9 Gy) for conventionally fractionated RT and the median margin dose was 14 Gy (range, 11-14 Gy) for GKS. Propensity score matching (PSM) was used to balance patient distributions between RT and non-RT groups.

Results: The RT group had higher percentage of patients with female gender, neurologic symptoms at presentation, petroclival location, Simpson grade IV-V, and tumor size ≥3.5 cm (all p < 0.05). At a median follow-up of 40.5 months, 5-year RFS and OS were 86.6% and 99.3%, respectively. In univariate analysis, petroclival location, tumor size, and Simpson grade showed significant correlations with RFS, while RT did not (p = 0.275). In multivariate analysis, tumor size (p = 0.047), Simpson grade (p < 0.001), and adjuvant RT (p = 0.007) have shown to be independently correlated with RFS. After PSM between RT and non-RT groups, the RT group showed better RFS than the non-RT group (5-year RFS, 100% vs. 51.4%, p = 0.009). Among the patients in the non-RT group, 3-year RFS for patients with 0 or 1 risk factor (low-risk group), 2 risk factors (intermediate-risk group), and 3 risk factors including petroclival location, tumor size ≥3.5cm, Simpson grade IV-V (high-risk group) were 95.9%, 59.7%, and 35%, respectively (p < 0.001). In a sub-group of 212 patients (84.5%) whose paraffin blocks were available to undergo immunohistochemical staining for Ki-67 labeling index (LI), petroclival location, tumor size, Ki-67 LI ≥2.26, and Simpson grade IV-V were significant variables in the univariate analysis while KI-67 LI (p = 0.015), Simpson grade (p<0.001), and adjuvant RT (p = 0.004) were independent prognostic factors for RFS.

Conclusion: Tumor size, surgical extent, Ki-67 LI and adjuvant RT were prognostic factors of RFS. The risk group-adapted approach may help select patients who could benefit from adjuvant RT following surgical removal of WHO grade I/II meningioma in the skull base.

Author Disclosure: S. Park: None. Y. Cha: None.

Sangjoon Park, MD

Yonsei University Health System

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