Pathological features determining recurrence and radioresistance in cerebral atypical meningioma

Abstract

We examined recurrence after gross total resection (GTR) or subtotal resection (STR) at St. Michael’s Hospital, Toronto, of 181 cases of atypical meningioma (WHO grade II). In the entire group, Kaplan-Meier survival curves showed that combined necrosis and brain invasion was the feature associated with the worst outcome, followed in order by necrosis, histological variants (clear cell, rhabdoid, and chordoid), high mitotic count, and brain invasion. The highly significant difference between necrosis and brain invasion and necrosis was seen only in patients receiving GTR, and lost in those treated with STR. Adjuvant radiotherapy was associated with worse outcome, more so in patients receiving GTR. In the presence of high mitotic count (defined as >4/10HPF) radiation did not affect recurrence, but necrosis and specially combined necrosis and brain invasion magnified the apparent deleterious effect of adjuvant radiotherapy. In the presence of brain invasion, radiotherapy’s small effect did not reach significance. Since patients were not randomized to adjuvant radiotherapy, these results should not be construed as indicating that this treatment is injurious. It can be stated that in the presence of necrosis and particularly necrosis and brain invasion, but not brain invasion alone, or high mitotic count, atypical meningiomas are more resistant to any possible beneficial effect of radiation in delaying recurrence.LEARNING OBJECTIVESThis presentation will enable the learner to: 1.Describe histological and treatment factors determining recurrence in atypical meningioma.2.List histological factors associated with radioresistance in atypical meningioma.