Patterns of relapse and growth kinetics of surgery- and radiation-refractory meningiomas.

Patients with surgery- and radiation-refractory meningiomas have a poor outcome. Due to our lack of knowledge concerning multi-recurrent meningioma natural history, their clinical course is poorly defined. This retrospective study aims at defining patterns of relapse in order to help in the definition of response criteria in future clinical trials. We performed a retrospective review of surgery- and radiotherapy-refractory meningioma cases with interpretable radiological follow-up treated in our department. Tumor volumes were measured on 3D T1 Gadolinium volumetric sequences using a semi-automated algorithm for tumor segmentation. Twenty nine patients with multi-treated meningioma (11 WHO Grade II, 5 de novo WHO Grade III and 13 transformed WHO Grade III), were evaluated. Median PFS was 16 months for patients with Grade II meningiomas. In patients with Grade III meningiomas, the de novo subgroup had a median PFS of 4 months compared with 7 months in patients with malignant transformation. Volumetric analysis of tumor growth concerned 95 tumor nodules in 50 relapses. The mean growth rate of tumor nodules was 10.4 cm(3)/year (95% CI 7.3-14.8 cm(3)/year). Three patterns of tumor growth were described: "classical" for 9 (31%) patients, "local multi-nodular" for 6 (21%) patients and "multi-nodular metastatic" for the last 14 (48%) patients. Considering all tumor nodules, median time to tumor progression (TTP) was 3.7 months. Progressing tumors represent the most frequent histological subgroup of surgery and radiation-refractory meningiomas while tumors with multi-nodular metastatic dissemination are the prominent radiological pattern of progression.