ESTRO 36 Abstract Book

S957 ESTRO 36 2017 _______________________________________________________________________________________________

6 Tata medical center, Psycho-Oncology, Kolkata, India 7 Tata medical center, Statistics, Kolkata, India Purpose or Objective There are no standard palliative breast radiotherapy regimens for local control but many use the dose equivalent as in the adjuvant setting (40Gy/15 fractions). Within HYPORT study we are exploring a dose of 35 Gy in 10 fractions over 2 weeks prescribed to the breast and supraclavicular fossa (SCF) to palliate advanced incurable breast cancers Material and Methods A gafchromic RTQA2 film based matching of the junction of tangents and Supraclavicular (SCF) fields (JF) is being carried out to assess the geographical overlap or separation during first 3 fractions. Similarly during the first 3 fractions, in-vivo thermo luminescent dosimetry (TLD) is being performed to confirm received dose by placing a TLD over isocenter of the tangential fields and another at JF. Primary objective for the study has been set to assess the acute toxicity using CTCAE version 4 in 30 total patients Results Of the required 30 patients, 19 have been recruited. Median dose planned to receive by 95% volume of the breast PTV was 96.3% (range=95.2-98.9%). The median dose max planned to the breast PTV was 106.4% (range=105.4-106.9%). Breast PTV receiving ≥105% of the prescribed dose was planned to be 1.75% (median) with no point dose ≥107%. Organ at risks (OAR) dose constraints were met for all patients. The junction movement range using gafchromic RTQA2 film was between -2mm to +3mm. TLD measured dose (median) and percentage variation of tangential field isocenter dose and field junction dose for first three fractions is summarized in table 1. Median percentage variation for tangential field isocenter dose as measured using TLD was 3 % (Range = -9.7 to 9.4%) and similarly median percentage dose variation for JF as measured with TLD was 1.2 %( Range= -8.5 to 8.9%). At a median follow up of 5 months only 1patient reported grade 2 acute skin toxicity (others had grade 1). None of the patients complained of dysphagia or acute brachial plexopthy Conclusion QA measures in the HYPORT study confirm the delivery of the prescribed two week dose schedule with no significant over dosage at the JF. A dose of 35Gy is well tolerated EP-1764 Implementation of a patient specific QA in- vivo dosimetry protocol using the PerFRACTION 3D system F. Vinagre 1 , P. Rachinhas 1 , P. Simões 1 , A. Cavaco 1 , F. Balau 1 , M. Borrego 1 1 Centro Hospitalar e Universitário de Coimbra, Department of Radiotherapy, Coimbra, Portugal Purpose or Objective The goal of this presentation is to share the experience in implementing an EPID-based in-vivo dosimetry system PerFRACTION™ 3D (PF) from Sun Nuclear Corporation in our center. The results for approximately 50 patients treated with VMAT and IMRT plans in a Truebeam 2.5, Varian Medical Systems, included in a in-vivo dosimetry protocol in clinical routine, are presented and discussed. Material and Methods About fifty patients treated with a VMAT/IMRT technique were included in this study. In the first 3 fractions of treatment, in-vivo EPID transit images (movie files) were acquired during treatment for every field. After the first 3 fractions, in-vivo measurements were repeated on a weekly basis. The PerFRACTION analysis is almost fully automated. Treatment plans were calculated in version 10.6 of Eclipse TM TPS from Varian Medical Systems. The plan, the structure set, the dose distribution and the CT image set are exported to PF server. This server

continually searches in R&V and ARIA TM oncology information system, from Varian Medical Systems, for the data of each patient. After each treatment the server gets the recorded log files and the measured EPID Dicom files which are processed and used for the 3D dose distribution calculation. PerFRACTION 3D uses a superposition/convolution type algorithm, the SDC Dose Calculator, to calculate back the dose on the CT image set or on the patient CBCT acquired at the treatment session. Following AAPM TG-218 report, we adopted a tolerance limit (treatable but further evaluation may be warranted) of 95 % of points passing the 3%Global/2mm/10% gamma analysis, and an action limit of 90% (requires additional analysis and may need corrective action). Dose-volume histograms (DVH) analysis obtained by 3D reconstructed dose on the planning CT or CBCT scans allow a clinical interpretation of the deviations and helps to find possible reasons for the discrepancies. PerFRACTION also demands goals definition for specific targets and/or organs at risk which are used to trigger failure email notifications. Results PerFRACTION 3D was launched in the beginning of 2016 and is in an early stage of clinical use, with constant software updates and corrections. In the first two months of the in-vivo dosimetry QA protocol implementation, 30 transit EPID images were acquired during the treatment fractions of 10 patients. PTV 3D overall gamma passing rate was equal to 97.3% ± 1% (1 SD), with all fractions within the adopted tolerance level of 95%. Conclusion The preliminary results for in-vivo dosimetry using PerFRACTION 3D suggests it as a promising tool for detection of treatment discrepancies and their clinical impact. This in-vivo dosimetry approach combined with plan pre-treatment verification can contribute to a more robust patient specific QA as well as to identify more clearly the possible causes of discrepancies such as machine and/or patient related ones. Electronic Poster: Brachytherapy: Breast EP-1766 First experiences using the new Papillon + TM Contact X-Ray Brachytherapy 50KVp (CXB) unit J.P. Gérard 1 , C. Dejean 2 , M.E. Chand 1 , D. Lam Cham Kee 1 , J. Doyen 1 , K. Benezery 1 , J.M. Hannoun-Levi 1 1 Centre Antoine Lacassagne, Radiotherapy, Nice, France 2 Centre Antoine Lacassagne, Physics, Nice, France Purpose or Objective The Papillon 50 TM unit was designed in 2009 to perform CXB treatment using 50 KVp X-Rays with short focus distance (FSD <4cm) and high dose rate (> 15 Gy/mn) aiming at replacing the Philips RT 50 TM to treat endoscopically rectal cancer. In order to treat breast cancer using an intra-operative radiotherapy (IORT) approach a new Papillon + TM ( P+ ) unit was designed (Ariane cpy. UK) and the first prototype was installed in Centre A Lacassagne in Nice during december 2016.