ESTRO 2022 - Abstract Book

S201

Abstract book

ESTRO 2022

(CTV2) which was expanded 0.5 cm to create phase 2 PTV (PTV2). RT dose of 14 Gy/7# was prescribed to PTV2. PET avid disease was demarcated as GTV PET and a margin of 3mm was given to generate PTV PET. PTV PET received escalated RT dose 21 Gy/7# using simultaneous integrated boost in phase 2 (Total dose 67 Gy/30 #). All patients received RT by VMAT along with concurrent and adjuvant TMZ. Following RT, patients who were lost to follow up, were contacted telephonically. The data was prospectively maintained in Microsoft Excel sheet. SPSS v 23 was used for statistical analysis. Figure 1 is showing (A) Pentixafor PET showing metabolically active disease; (B) Target volume delineation ; (C)

Phase 1 dose colour wash; (D) Phase 2 dose colour wash including SIB

Results

A total of 20 patients were analysed. Patient and treatment characteristics have been shown in table 1. Median follow up was 23 months (20.8 ± 7.97). Fourteen patients had documented recurrence and succumbed to the disease. A median overall survival (OS) of 23 months (95% CI, 17.15-28.8) was observed with estimated 1, 2 and 3 years OS of 80%, 43.7% and 0% respectively. A significant association of OS was seen with extent of surgery (0.04). A non-significant trend towards increased OS was seen in those with KPS >70, age <40 years and >6 cycles of TMZ. No patient developed symptomatic radiation necrosis. Conclusion Although radiotherapy dose escalation remains challenging in GBM, latest technologies can help in targeting the metabolically active tumor with higher dose without increasing the risk of radiation necrosis. The index study shows slightly higher median OS as compared to the historical data indicating that radiotherapy dose escalation is feasible and well tolerable in GBM patients and should be further explored in the randomised trials.

PD-0240 Development of mid-treatment biological image guided adaptive radiotherapy (BIGART) for glioblastoma

M. Gupta 1 , L. Mancini 2 , S. Bisdas 2 , S. Manolopoulos 3 , M. Kosmin 1

1 University College London Hospitals NHS Foundation Trust, Department of Radiotherapy, London, United Kingdom; 2 National Hospital for Neurology and Neurosurgery, University College London Hospitals NHS Foundation Trust, Lysholm Department of Neuroradiology, Neuroradiological Academic Unit, Department of Brain Repair and Rehabilitation, IoN, UCL, London, United Kingdom; 3 University College London, Department of Physics and Bioengineering, London, United Kingdom