Similar Local Control Rates for Patients with Meningiomas Treated with Proton Therapy vs. IMRT

Abstract

To characterize the outcomes associated with fractionated proton or photon therapy for the treatment of meningiomas. We reviewed the records of 136 patients treated with RT at our institution between 2000 and 2014. Seventy-five (55%) patients received IMRT and 61 (45%) received PBT. The median age of patients was 54 years (57 years IMRT vs. 49 years PBT, P=0.003), while the majority were female (66%) and White (71%). Eighty seven (64%) had base of skull involvement with no differences between PBT and IMRT (P=0.29). Initial treatment for the majority of patients was surgical resection (n=93, 68%) with about half receiving postop RT (45%). Forty three (32%) patients received definitive RT without resection and 51 patients (38%) were treated at the time of recurrence to gross disease. RT was delivered to a median tumor size of 3.0 cm (range, 0.7-11.6) for patients with measurable disease. The median dose was 50.4 GyRBE in 28 fractions. Median follow-up time was 67 mon (range, 0-190; IMRT 91 mon vs. 54 mon, P<0.001) with a 5y OS of 79%. Sixteen (12%) patients developed a LF at a median time of 35 mon (range, 1-63), of which 10 (63%) were in-field, 3 (19%) marginal, and 3 (19%) out-of-field. There was no difference in the actuarial LF rate between PBT and IMRT when stratified by tumor grade (Grade 1: 5y LF 4% [PBT] vs. 6% [IMRT], P=0.35; Grade 2: 5y LF 43% [PBT] vs. 42% [IMRT], P=0.55; Grade 3: 3y LF 0% [PBT] vs. 25% [IMRT], P=0.48), or the median time to recurrence (31 mon [PBT] vs. 48 mon [IMRT], P=0.23) between modalities. As is apparent based on actuarial LF rates, grade 2 (n=11, 52%) and grade 3 (n=1, 13%) had a higher incidence of LF than grade 1 tumors (n=4, 4%; P<0.001). Interestingly, no patients that received definitive RT in the absence of resection (either biopsy only or no tissue acquired) recurred locally, compared with 10 patients receiving postop RT and 6 receiving RT for a gross recurrence (P<0.001). RT modality was not significantly associated with LF on multivariate analysis; the only factors associated with a higher LF rate on multivariate analysis included: grade 2 (HR 14, P<0.001, 95% CI 3.7-49.8) and grade 3 tumors (HR 184.0, P<0.001, 95% CI 11.8-2864.1), as well as larger tumor size (continuous variable, HR 1.43, P=0.003, 95% CI 1.13-1.82). Thirty seven (27%) patients had at least one late toxicity, the majority of which were grade 1-2 (n=24, 65%); there were no grade 5 toxicities. There was no difference between PBT and IMRT in the incidence of grade 1-2 late toxicities (68% vs. 58%) versus higher grade toxicities (32% vs. 42%, P=0.72). Our study demonstrates equivalency in local control for patients receiving PBT compared to IMRT with no significant difference in higher grade toxicities. Furthermore, no patients receiving definitive RT (either biopsy proven grade I or un-biopsied tumors) developed local recurrence.