Stereotactic Radiotherapy for Trigeminal Schwannomas

Abstract

Data on radiotherapy for trigeminal schwannomas (TSs) and comparison of stereotactic radiosurgery (SRS) with fractionated stereotactic radiotherapy (FSRT) are limited. We present a large retrospective review of our institutional experience treating TSs with SRS and FSRT. We also describe a flare phenomenon experienced by some patients. The records of 23 consecutive TSs patients treated with radiotherapy between 1996 and 2011 were reviewed. We investigated radiographic response, tumor control, and toxicity. Ten patients underwent SRS and 13 underwent FSRT, with median clinical follow-up of 32 months (range, 3-120 months). Tumor control at 5 and 10 years was 94% overall. Symptom control at 5 years was achieved in 48% of all patients, with nonsignificant improvement in more patients in the FSRT group than those in the SRS group (56% vs 40%, P = .37). Acute toxicity was higher in the FSRT group (38.5 vs 0%, P < .01), although lesions treated with FSRT were larger (mean, 9.5 mL vs 4.8 mL, P < .01). A symptomatic flare phenomenon occurred in 2 patients (8.7% overall) during FSRT, involving transient cystic formation and dramatic size increase. One lesion regressed in size and 1 remained stable on follow-up. Tumor control rates for TSs are excellent with SRS and FSRT with minimal toxicity. This represents the first documented report of a flare phenomenon after FSRT for TS treatment. Flare risk after FSRT in previously resected large lesions should be discussed with patients before treatment, and prophylactic oral steroids may be considered.