Abstract Book

S1246

ESTRO 37

EP-2381 Evaluation of reduced PTV margins for IGRT and IMRT of esophageal cancer M. Michalet 1 , F. Castan 2 , O. Riou 1 , C. Lemanski 1 , C. Llacer-Moscardo 1 , O. Lauche 1 , D. Azria 1 , N. Aillières 1 , J. Prunaretty 1 1 CRLC Val d'Aurelle/Paul Lamarque, Radiothérapie, Montpellier Cedex 5, France 2 CRLC Val d'Aurelle/Paul Lamarque, Unité de biométrie, Montpellier Cedex 5, France Purpose or Objective To demonstrate the feasibility of reduced PTV margins of 5 mm for Intensity Modulated Radiotherapy (IMRT) in esophagus cancers using Image Guided Radiotherapy (IGRT). Material and Methods Patients who underwent IMRT in 2016 at the Institute of Cancer of Montpellier, for a primitive cervical or thoracic esophageal cancer, of any TNM stage and histology, were included. Reduced isotropic PTV margins of 5 mm were retrospectively studied. The IGRT was carried out daily, either with kV-kV or either with Cone Beam CT (CBCT). Image registration was done by radiation therapists. Tumor coverage with reduced PTV margins was retrospectively assessed by a physician on every CBCT registration. Differences between radiation therapist and physician registrations were checked. Results 30 patients treated between the 09/02/2015 and the 01/18/2017 were included. There were 18 squamous cell carcinomas (60%), 8 adenocarcinomas (27%) et 3 neuroendocrine carcinomas (10%). The localization was thoracic esophagus in 93% of cases (10% the upper third, 33% the middle third, 30% the lower third, 20% the middle et lower third), and cervical in 7% of cases. 145 CBCT registrations were retrospectively assessed (2 to 5/ patient, maximum 1/week randomly determined). The tumor was covered by the PTV in 61% of the cases before CBCT and in 95% of cases after CBCT. The tumoral coverage was not obtained in 7 CBCT, corresponding to 5 different patients. The registration differences were less than 5 mm in 96% of the cases. The differences were greater for the lower third of the thoracic esophagus.

in breath-hold and appropriate selection of user- definable variables such as type of CBCT scan, kV/mAs values, reconstruction matrix and slice-thickness can help improve visibility in individual patients (Figure). A CBCT was performed between arcs to increase opportunities for positional verification/re-positioning. Treatment time: in 8 patients (4 left/4 right glands), treated with 7.5Gyx8 (n=3), 5Gyx12 (n=4) and 3Gyx15 (n=1), the mean (SD) for total treatment, beam-on and IGRT times were 12.0 (3.2) min, 2.2 (0.5) min and 9.9 (3.3) min respectively. The median (mean) number of CBCT scans/fraction was 3 (3.4) scans.

Conclusion High-dose adrenal radiotherapy can be efficiently performed on a standard LINAC using CBCT guidance. Simple steps can be taken during treatment planning and IGRT to help minimize treatment risks. EP-2380 Feasibility and efficacy of SIB-IMRT based on MRI-CT fusion in NSCLC patients with brain metastases W. Huang 1 , Y. Dong 2 1 Shandong Cancer Hospital, Radiation Oncology 6, Jinan, China 2 University of Jinan-Shandong Academy of Medical Sciences, School of Medicine and Life Sciences, Jinan, China Purpose or Objective To assess the feasibility and therapeutic effects of simultaneous integrated boost intensity-modulated radiation therapy (SIB-IMRT) based on the fusion imaging of magnetic resonance imaging (MRI) and computed tomography (CT) as a dose-intensive technique in patients with brain metastases (BM) of non-small cell lung cancer (NSCLC). Material and Methods Twenty-eight NSCLC patients with 1 to 7 brain metastases were enrolled in this retrospective study between November, 2011 and February, 2015. Twenty patients (71.4%) had 1-3 metastases (oligometastases), otherwise, more than 3 metastases were seen in only 8 patients (28.5%). GTV (Gross tumor volume) contouring was based on the fusion imaging of MRI-CT, WBRT was prescribed in 37.5 Gy/15 fractions with a simultaneous boost in the metastatic lesions of 52.5 Gy/15 fractions. Results The median overall survival (OS) and intracranial progression free survival (PFS) for all the patients were 21.0 months and 14.0 months, respectively. The 6-month and 1-year OS were 78.6% and 46.4% respectively, while the 6-month and 1-year PFS were 67.9% and 21.4% respectively. Until the end of the follow-up, 17 patients (60.7%) were alive. No evidence of intracranial progress or recurrence was found in 10 patients (35.7%) during the

Example of errors with only bone-based registration :

follow-up. Conclusion

SIB-IMRT with the dose/fractionation based on the fusion imaging of MRI-CT is feasible and safe. It is beneficial to the NSCLC patients with BM and can reduce the overall costs of treatment.