ESTRO 2022 - Abstract Book

S636

Abstract book

ESTRO 2022

Materials and Methods Data were retrospectively collected from a cohort of patients (pts) who underwent HS-WBRT from 2016 to 2021. Inclusion criteria were: 1) diagnosis of BM; 2) Karnofsky Performance Status (KPS)> 60; 3) life expectancy more than 6 months; 4) available brain magnetic resonance imaging (MRI) before RT; 5) signed written informed consent. Treatment was performed using TomoHelical scheduled in 30 Gy in 10 or 12 fractions or 25 Gy in 10 fractions (Figure 1). Oncological outcomes were clinically and radiologically assessed every 3 months after the end of HS-WBRT. First, Kaplan-Meier plots depicted oncological outcomes rates and univariable and multivariable Cox regression models focused on predictors of local progression. Encephalic progression-free survival was analyzed considering as competing risks systemic progression and death before first radiological assessment. Toxicity was graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0. Results One-hundred and nineteen pts matched inclusion criteria. Eighty-eight percent had KPS 90-100, 12% KPS 60-80. More represented primaries were NSCLC (39%) and breast (53%). The majority of patients had ≥ 10 BM. Median dose to hippocampus was 7.6 Gy (range 6.41, 12.5), median volume was 2.03 cc (range 0.64, 4.95) and median maximum dose was 13.4 Gy (range 8.74, 27.1) ( Figure 1 ). Most of pts (60%) underwent concomitant systemic therapies. Forty patients (34%) experienced a brain recurrence. Of them, 57% were exclusively extra-hippocampal and 40% had intra-hippocampal involvement. Forty-two percent were oligoprogression (maximum 5 lesions), and 16 involved hippocampi. Median time to recurrence was 7 months (range 0-23). After a median follow up of 17.15 months (range 0-49), 74% of patients were dead. Patients who underwent concomitant systemic therapy (n=71) were stratified according to the treatment (chemotherapy vs others) and results showed a benefit for not chemo systemic treatments in terms of OS and any PFS (p= < .001), but not in terms of local control (p= .12) ( Figure 2 ). No acute toxicities ≥ G2 were observed on the entire cohort.

Conclusion Given the growing potential for prolonged survival with metastatic disease, identifying strategies to reduce treatment- associated side effects is of increasing significance. In the present study, according with published literature, HS-WBRT shows a durable intracranial disease control. A small risk of additional intra-hippocampal recurrence seems to be justified by memory preservation reported in numerous studies on HS-WBRT.

MO-0726 Volumetric change in gray matter after radiotherapy in glioma patients detected with MRI

H. Lee 1 , M.K. Kang 2 , K. Hwang 3 , C. Kim 3 , Y.J. Kim 4 , K.J. Suh 4 , B.S. Choi 5 , I.A. Kim 6 , B. Jang 6

1 Seoul National University Hospital, Department of Radiation Oncology, Seoul, Korea Republic of; 2 Nowon Eulji Medical Center, Eulji University, Department of Neurology, Seoul, Korea Republic of; 3 Seoul National University Bundang Hospital, Department of Neurosurgery, Seongnam, Korea Republic of; 4 Seoul National University Bundang Hospital, Department of Internal Medicine, Seongnam, Korea Republic of; 5 Seoul National University Bundang Hospital, Department of Radiology, Seongnam, Korea Republic of; 6 Seoul National University Bundang Hospital, Department of Radiation Oncology, Seongnam, Korea Republic of

Purpose or Objective