Radiation-associated grade 2 meningiomas: A nine patient-series and review of the literature.

INTRODUCTION Radiation-associated meningiomas (RAM) remain rare but recognized to harbor a high potential of aggressiveness. Only few studies focused on grade 2 histological variants. OBJECTIVE Our study aims to report the natural history of patients with radiation-associated grade 2 meningiomas followed in a single institution. MATERIALS AND METHODS This retrospective study included all patients with grade 2 RAM operated in our institution between 1994 and 2011. We used the WHO 2007 classification for histological grading. The degree of resection was evaluated using Simpson Classification. The tumor was considered radiation-associated, if the patient had a medical history of cranial irradiation for another medical condition (1 year before at least). Patients benefited from a post-operative close clinical and radiological (cranial MRI) follow-up every 4 months during 2 years and annually thereafter, to detect any tumor progression. Adjuvant therapy and/or monitoring were systematically decided during a multidisciplinary team meeting. RESULTS Nine patients (6 men and 3 women) were included in the study. The mean age at diagnosis was 34 years old (range 20-55 years). The mean follow-up was 77 months (range 31-180 months). The mean delay between initial cranial radiation therapy and the diagnosis of grade 2 RAM was 23 years (range 16-33 years). Among all patients, 4 harbored a meningiomatosis, while 5 patients harbored a single tumor. Post-operative local tumor progression was noted in 4 patients. Progression free survival (PFS) after the first surgery in these 4 patients was 15, 23, 35, and 47 months. In these 4 progressive patients, 7 surgical resections, 3 GKS and 1 fractionated radiation therapy have been performed. Post-operative tumor progression was noted at distance from the operated meningioma in 1 patient with meningiomatosis. At final control, 2 patients had severe oculomotor palsy and 1 patient needed palliative cares related to progressive meningiomatosis with anorexia and swallowing disturbance. CONCLUSION Grade 2 RAM is a severe radiation-associated disease occurring preferentially in younger male patients. Although, surgery remains the mainstay treatment, the high potential of tumor progression often requires adjuvant therapeutic tools. Thus, new radiation therapy should be discussed in some cases and the role of radio surgery is still to be better defined.