Phase 2 trial of observation for low-risk and radiotherapy for intermediate and high-risk meningioma: long-term analysis

The multicenter phase 2 NRG Oncology RTOG 0539 trial evaluated observation for low-risk meningioma and radiotherapy (RT) for intermediate- and high-risk meningioma. Low-risk (group 1; n=60) was defined as grade 1 tumor after gross total resection or subtotal resection (GTR/STR). Intermediate-risk (group 2, n=52) was defined as recurrent grade 1 or newly diagnosed grade 2 tumor after GTR. High-risk (group 3, n=53) included newly diagnosed grade 2 tumor after STR, newly diagnosed grade 3 tumor, or recurrent grade 2 or 3 tumor. Group 1 was prospectively monitored, group 2 received 54 Gy, and group 3 received 60 Gy. The median follow-up time for the three cohorts were 12.1, 12.0, and 11.1 years. The ten-year PFS and OS rates for groups 1, 2 and 3 were 85.2% and 94.1%, 72.2% and 84.7%, and 42.5% and 51.1%, respectively. Five patients in group 2 (9.6%) and eight patients in group 3 (15.1%) had grade 3+ toxicity attributed to RT. The authors conclude that the long-term outcomes support this risk-adapted approach.