ESTRO 2024 - Abstract Book

S807

Clinical - CNS

ESTRO 2024

progression. The median total dose was 59.4Gy (47.5-60Gy). Within this cohort, 4 patients had received prior radiotherapy for meningioma at sites distant to the present target volume. With a median follow-up of 61.3 months [95% (Confidence interval, CI): 50.0-72.5], the 5-year progression-free survival (PFS) and overall survival (OS) rates for the study cohort were 88.7% [95%CI: 81.8-96.1] and 91.4% [95%CI: 85.3-97.9], respectively. Estimated 5-year local control (LC) for WHO grade I, II and III cases were 92.8%, 74.5% and 71.4% respectively (p=0.0026). Multivariate analysis indicated that histology WHO grade > I (p=0.019) as well as timing of PBT (recurrent or progression cases) (p=0.037) were covariates significantly associated with disease progression. A total of 13 (8.5%) patients had relapses during follow- up, all of whom had recurrent lesions within the 90% isodose line (defined as “in field”), four of them had coexisting recurrences outside the 90% but within the 50% isodose line (defined as “marginal”) and 3 of the 13 patients also had relapses in combination with “distant” failure (outside the 50% isodose line). Acute toxicities of CTCAE grade 3 were detected in 5 (3.3%) patients, of those, pain (n=1) and dermatitis (n=1, occurred at the week 6 of PBT) were newly onset, two patients had gait disturbance progressed from grade 2 and one patient’s headache deteriorated from grade 1. No grade ≥4 acute toxicity was observed. Nineteen patients (12.4%) developed CTCAE ≥ grade 3 late adverse events of impaired visual function during long-term follow-up (new adverse event n=14; deterioration n=5), including an abnormal optic nerve function (Grade 4, n=1; Grade 3, n=4), decreased visual acuity (Grade 4, n=6; Grade 3, n=4), eyelid anomalies (Grade 3, n=2), diplopia (Grade 3, n=1) and dry eye (Grade 3, n=1). Hearing impairment occurred in 4 patients (Grade 3, n=4).