High-dose radiation therapy using photons and carbon ion radiotherapy in patients with atypical and anaplastic meningiomas: Relevance of neuropathologic classification and therapeutic impact of a boost using of carbon ion radiotherapy.

Abstract

2071 Background: Histology reevaluation and correlation with outcome after photon and carbon ion radiotherapy (RT) was performed in 73 patients with atypical or anaplastic meningiomas. Methods: Twenty-seven patients were treated with FSRT, 7 with IMRT and 8 patients with a carbon ion boost. All other patients were treated with 3D-conformal photon RT. The tumor specimens of 66 patients were acquired for review and H&E, reticulin, and IHC for Mib1, EMA, CD34, Lu5, INI1, GFAP were performed. In 4 cases the initial diagnosis was not reproducible. Overall survival (OS) and progression- free survival (PFS) were analyzed. Impact of RT dose was evaluated. Results: Re-evaluation resulted in an identical grading in 25 tumors, a downgrading of 1 grade in 28 patient, downgrading of 2 grades in 8 patients, and in upgrading of one grade in 1 tumor. Therefore, 17 patients were graded as benign meningiomas WHO grade I, 32 patients as atypical meningiomas WHO grade II, and 13 patients as anaplastic meningiomas. According to the 1993-classification, OS rates were 95.3% at 5 years for grade II, and 63% at 5 years for grade III meningiomas (p = 0.02). After re-evaluation, tumors of 10 patients were downgraded to grade I. with an OS of 100%; for grade II, OS was 73% at 5 years, and 42% at 5 years for grade III tumors (p = 0.009). Patients initially graded as anaplastic (n = 39) were subdivided after re-evaluation into grade I, II and III, showed a significant difference in OS (p = 0.03). PFS was 60% at 5 years for grade II, and 32% for grade III tumors (p = 0.03). After re-evaluation, PFS for grade II was 43% at 5 years; for grade III, PFS was 8% at 5 years (p = 0.02). In the group treated with carbon ion RT low toxicity and higher survival rates of 75% and 63% at 5 and 7 years was seen. Conclusions: Postoperative RT is recommended for high risk meningiomas. With the new classification, standardized evaluation is possible. Carbon ion RT offers an excellent mode of dose-escalation in patients with high-risk meningiomas and will be evaluated in a prospective trial at the Heidelberg Ion therapy Center (HIT; MARCIE-Trial). No significant financial relationships to disclose.