ESTRO 2020 Abstract Book

S345 ESTRO 2020

Conclusion Edits to DLC contours are generally small, but exhibit variability, with volumetric differences which may lead to DVH and treatment plan variability. Nevertheless, systematic editing, apparent for some clinical DLC contours, may help to identify regions where DLC can be retrained, further reducing human intervention in the segmentation process. Future work will focus on automated methods to decrease clinical variability in editing, using this data to inform the training of future models and predicting the clinical editing of auto contours.

Results Between Apr 2010 and Sep 2017, 150 patients were included in 7 institutions. The trial was closed after randomization of 107 patients (initial target 164): 54 to armA and 53 to armB. Patient characteristics are summarized in Table1. Median FU for FFLF was 12.6 months (IQR 5.2-24.6). Median escalated prescribed dose to the PTV whole tumor (armA) was 3.25 Gy per fraction (IQR 3.13-3.40), and median total dose was 78.0 Gy (IQR 75.0-81.6). Median prescribed dose to the PTV 50%SUVmax (armB) was 3.50 Gy per fraction (IQR 3.35-3.90), and median total dose was 84.0 Gy (IQR 80.4-93.6). 72% of patients received concurrent chemo-radiotherapy. Central review showed that the PT was non-measurable in 27% of CT-scans (96/352), mainly due to inflammation, fibrosis and/or atelectasis. If lesions remained stable over time, this was scored as no local failure. In the first year, 22 patients died without known local failure, 16 were lost to CT follow-up and 8 were not-evaluable. The 1-year FFLF rate in evaluable patients was 97% (95% CI 91-100) in armA, and 91% (95% CI 82-100) in armB. The 1- and 3-year OS rates were 77% and 37% in armA, and 62% and 33% in armB, respectively. FFLF and OS curves are shown in Figure1.

Plenary Session: Highlights of Proffered papers (late- breaking abstracts)

OC-0609 The PET-boost trial: isotoxic homogeneous or FDG-directed dose escalation in stage II-III NSCLC S. Cooke 1 , D. De Ruysscher 2 , B. Reymen 2 , M. Lambrecht 3 , G. Fredberg Persson 4 , C. Faivre-Finn 5 , E. Dieleman 6 , R. Lewensohn 7 , J. Van Diessen 1 , K. Sikorska 8 , F. Lalezari 9 , J. Sonke 1 , J. Belderbos 1 1 netherlands Cancer Institute, Department Of Radiation Oncology, Amsterdam, The Netherlands ; 2 maastricht University Medical Centre, Department Of Radiation Oncology Maastro Clinic- Grow – School For Oncology And Developmental Biology, Maastricht, The Netherlands ; 3 ku Leuven – University Of Leuven, Department Of Oncology- Experimental Radiation Oncology, Leuven, Belgium ; 4 rigshospitalet - University Of Copenhagen, Department Of Oncology, Copenhagen, Denmark ; 5 the Christie Nhs Foundation Trust - University Of Manchester, Department Of Clinical Oncology, Manchester, United Kingdom ; 6 amsterdam Umc - University Of Amsterdam, Department Of Radiation Oncology, Amsterdam, The Netherlands ; 7 karolinska Institute, Department Of Radiation Oncology, Stockholm, Sweden ; 8 netherlands Cancer Institute, Department Of Biometrics, Amsterdam, The Netherlands ; 9 netherlands Cancer Institute, Department Of Radiology, Amsterdam, The Netherlands Purpose or Objective The randomized phase II PET-boost trial(NCT01024829) aimed to improve freedom from local failure(FFLF) by boosting either the whole primary tumor(PT) or the high FDG uptake region inside the PT(> 50%SUV max ) in non-small cell lung cancer (NSCLC) patients. Here we report on the primary endpoint FFLF at 1 year, and secondary endpoint overall survival(OS). Material and Methods Eligible patients had stage II-III NSCLC with a primary tumor ≥4 cm, SUV max ≥5.0 and WHO PS ≤ 2. For each patient, before randomization, a treatment plan (24x2.75Gy) was made for both arms with a simultaneously integrated boost to the whole PT (armA) or to the PT 50%SUV max area (armB). The boost dose (up to 5.4 Gy per fraction) was maximized by normal tissue constraints while the mean lung dose of the two plans was normalized. In case dose escalation of ≥3 Gy per fraction was not possible, patients were not randomized. Response was assessed with (PET/)CT at 3, 6, 12 and 18 months. All CT-scans were centrally reviewed by a dedicated radiologist. Local failure was defined as 20% growth from nadir (akin to RECIST). The trial was powered(one sided α=0.05;β=0.80) to detect an increase of FFLF at 1 year from 70% (historical rate) to 85%, requiring 82 randomized patients in each arm.