2560 - Safety Analysis of a Prospective Phase 2 Trial of Hypofractionated Proton Therapy for Benign Intracranial Tumors
Presenter(s)
N. Bader1, M. W. McDonald2, H. K. G. Shu3, Y. Liu4, J. Zhong3, K. B. Hoang5, E. Nduom5, J. J. Olson6, and B. R. Eaton3; 1Emory University School of Medicine, Atlanta, GA, 2Winship Cancer Institute of Emory University, Atlanta, GA, 3Department of Radiation Oncology, Winship Cancer Institute of Emory University, Atlanta, GA, 4Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, 5Department of Neurosurgery, Emory University School of Medicine, Atlanta, GA, 6Departmetnt of Neurosurgery, Winship Cancer Institute of Emory University, Atlanta, GA
Purpose/Objective(s): Conventionally fractionated radiation therapy (RT) delivered over 5-6 weeks is standard of care for many benign brain tumors not amenable to radiosurgery. Shorter treatment courses may be preferred by patients and may lessen the social impacts and financial costs of care. The purpose of this analysis is to report treatment associated toxicity and early clinical outcomes for patients enrolled on a prospective phase 2 trial of moderately hypofractionated proton therapy (NCT04278118).
Materials/Methods: Eligible patients were = 18 years old with biopsy confirmed or radiographically diagnosed benign intracranial tumors, and meningiomas of any grade without prior overlapping RT. Radiographically diagnosed or WHO Grade 1 lesions were treated to 42.5 Gy (RBE) in 17 fractions and WHO grade 2-3 lesions were treated to 50-55 Gy (RBE) in 20 fractions. Toxicity was graded using the Common Terminology Criteria for Adverse Events (CTCAE v5). Patient reported outcomes related to cognition and fatigue were collected using Patient-Reported Outcomes Measurement Information System (PROMIS).
Results: Thirty-two patients were enrolled from 3/2020 – 10/2024. Median age was 61 (range 31-86) Most patients were female (n = 25) and identified as white (n = 25) with a diagnosis of meningioma (n=22) or schwannoma (n = 6). Patients were treated with pencil beam scanning proton therapy except one patient received VMAT due to insurance denial. Twenty-six (81%) patients were treated to 42.5 Gy (RBE), and 6 patients with WHO grade 2 meningiomas were treated to 50 Gy (RBE); 3/6 with a simultaneous integrated boost to gross residual disease to 55 Gy (RBE). The average lesion size (maximum dimension) for those with gross tumor was 3.0 cm. Seven acute grade 2 events (22%) included fatigue, headache, tinnitus, pain, and hair loss. Three late grade 2 events (9%) included trigeminal neuralgia, blurry vision, and headache. No acute or late grade 3+ events were seen. Additionally, there were no significant changes from baseline to 4-weeks (n = 19), 3-months (n = 20), or 1-year (n = 12) in the PROMIS cognitive domain (all p > 0.05). There was an increase in fatigue at 4-weeks post-treatment as compared to baseline (p = 0.03) but no difference at the 3-months follow-up. Among 24 patients with > 3 months follow-up at our institution, median follow-up is 24 months (range 3-49 months). Two patients had local progression: one patient with recurrent WHO grade 1 meningioma progression marginal to the treatment field at 31-months, and one patient with a radiographically diagnosed meningioma had local progression at 29-months.
Conclusion: Hypofractionated proton therapy for benign brain tumors shows an excellent safety profile on this ongoing single institution prospective trial. Early local control outcomes appear to be acceptable, though longer follow-up for more patients are needed to confirm these results. Hypofractionation may decrease the time and financial toxicity associated with longer treatment regimens for these CNS tumors.