ESTRO 2023 - Abstract Book

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ESTRO 2023

Results In our center, 168 pts (64% female, 36% male) with BM were treated with PT. The median age was 55 years (range, 15-86). One hundred-eight (64%) pts received PT after surgery or biopsy, in adjuvant setting or for relapse: 74 BM were WHO I and 29 were WHO II-III, while in 5 pts WHO grade was unknown. Neither surgery nor biopsy was performed in 60 (36%) pts. PT was delivered, with a median total dose of 55.8GyRBE (range, 50,4–66) and a median dose/fraction of 1.8GyRBE (range 1.8–3.6). Median ccGTV and ccCTV were 15.6 cmˆ3 (range, 0–324) and 30.5 cmˆ3 (range, 3.1–354), respectively. Median follow-up was 40 months (range, 6-99). Ten pts had a local relapse after a median time of 40 months (range, 13 50). All but one local recurrence occurred in grade WHO II-III pts. 5-y LC and 5-y PFS were 98.1% and 90.7% in WHO I and no surgery group, respectively. Furthermore, WHO II-III group 5-y LC and 5-y PFS were 53.0% and 42.3%. WHO II-III group, respectively. Two acute G3 RIAEs were reported (dermatitis radiation and edema cerebral). Late RIAEs were reported in Table 1. All grade brain radionecrosis was reported in 25 (15%) pts; 2 and 3 of them experienced G2 and G3 brain toxicity, respectively. No G4-G5 acute and late RIAEs were highlighted. At univariate analysis, no significant impact of PT site (skull-base or other intracranial localization, p = 0.84) and of ccGTV (p = 0.19) on late RIAEs >G2 in each domain were detected.

Conclusion PT can be considered a valuable treatment option for BM pts due to the high rate of LC with minimal side effects.Moreover, PT seems to be an effective and safe treatment also when it is given in progressive and pre-treated diseases. These results prompt to explore the role of PT in prospective trials with longer follow-up.

PO-1127 Dose-response relationship in patients with atypical meningioma treated with adjuvant radiotherapy

D. Kim 1,2 , W.I. Chang 1 , H.K. Byun 3 , I.A. Kim 1,4 , J. Cho 3 , J.H. Lee 2 , H.I. Yoon 3 , C.W. Wee 1,5

1 Seoul National University College of Medicine, Radiation Oncology, Seoul, Korea Republic of; 2 Seoul National University Hospital, Radiation Oncology, Seoul, Korea Republic of; 3 Yonsei Cancer Center, Yonsei University College of Medicine, Radiation Oncology, Seoul, Korea Republic of; 4 Seoul National University Bundang Hospital, Radiation Oncology, Seongnam, Korea Republic of; 5 SMG-SNU Boramae Medical Center, Radiation Oncology, Seoul, Korea Republic of Purpose or Objective This study aimed to identify the radiation dose-response relationship in patients with newly diagnosed atypical meningioma (AM) treated with adjuvant radiotherapy (ART) using conventional fractionation. Materials and Methods A total of 158 patients who underwent surgery and ART between 1998 and 2018 were reviewed. Among those, 135 patients with complete information on radiotherapy (RT) dose/fractionation and pathological reports were analyzed. We entered RT dose as a continuous variable into the Cox regression model using penalized spline to allow for a non-linear relationship between RT dose and events. Local control (LC), progression-free survival (PFS), and overall survival (OS) were evaluated. The corresponding biological equivalent dose in 2 Gy fractions (EQD2) was calculated using an α / β ratio of 4 Gy.

Results