ESTRO 2023 - Abstract Book

S415

Sunday 14 May 2023

ESTRO 2023

The results have provided an assessment of the magnitude of the correction factors, to account for lack of scatter, non water equivalence of the phantom, dosimeter and the influence of the table material as compared to TG-43 conditions. Validations of these results using commercial model-based dose calculations are underway. PD-0506 Characterization of a novel gamma camera for live source localization in HDR brachytherapy J. Strotmann 1 , A. Sipahi 2 , K. Büsing 3 , W. Kunth 3 , N. Chofor 4 , B. Poppe 3 , A. Patil 5 , A.A. Schönfeld 4 1 Carl von Ossietzky University, University Clinic for Medical Radiation Physics, Oldenburg, Germany; 2 Heinrich Heine University, Department of Radiation Oncology, Duesseldorf, Germany; 3 University Clinic of Medical Radiation Physics, Medical Campus Pius-Hospital, Oldenburg, Germany; 4 Sun Nuclear, A Mirion Medical Company, Research & Development, Melbourne, USA; 5 Mirion Technologies, Inc., Research & Development, Meriden, USA Purpose or Objective By combining a visual video camera with a gamma camera, the novel HDR-Vue system provides real-time visualization of the source location in a HDR brachytherapy treatment room. The aim of the present work was to investigate the capabilities of the system for the localization of the HDR source. Materials and Methods A Ir-192 source (A = 345–239 GBq) was scanned across the 30° by 40° field of view (FOV) of the gamma camera of a prototype HDR Vue system (Mirion Technologies, Atlanta, USA) in a 10 mm grid using a motorized water phantom with a custom-made mounting system. Thereby, camera-to-source distances of 500, 700, and 1000 mm in air, as well as water depths of 30, 50, 100, and 150 mm were investigated at a dwell time of 5 s to mimic clinical scenarios. The mean source position and the corresponding standard deviation were determined based on the recorded video frames, where the water phantom’s coordinate system served as reference. The entire FOV could thus be characterized with regards to localization accuracy of the source in air and in water. Results The standard deviation of the detected source position was below 2 mm at the center of the image and increased with increasing source to camera distance, viewing angle and depth in water. An accuracy of better than 10 mm standard deviation across the full FOV is achieved for water depths of up to 50 mm at a source to camera distance of 500 mm. At a depth in water of 120 mm, a 10 mm standard deviation is still achievable within an FOV of 6°. Conclusion The HDR-Vue provides real-time localization of the Ir-192 source during the treatment and may benefit the detection of gross errors in HDR brachytherapy, as well as provide useful information for emergency recovery scenarios. OC-0507 Comparison of quality of life among Carcinoma tongue patients treated with EBRT alone and EBRT & BT V. Anand 1 , M. Lala 2 , V. Babu 1 , S. Deshpande 1 , K. Venkatesan 1 , S. Pradhan 3 1 P D Hinduja Hospital and Medical Research Centre, Radiation Oncology, Mumbai, India; 2 P D Hinduja Hospital and medical research centre, Surgical Oncology, Mumbai, India; 3 P D Hinduja Hospital and Medical Research Centre, Surgical Oncology, Mumbai, India Purpose or Objective To compare the health-related quality of life (QOL) in patients with carcinoma tongue treated with external beam radiation therapy (EBRT) alone versus EBRT to the neck and radical high dose rate brachytherapy (HDR-BT) to the tumor bed. Materials and Methods 63 tongue cancer patients who underwent surgery followed by adjuvant radiotherapy either in the form of EBRT alone or EBRT and HDR-BT from January-2015 to October-2021 were included in this study. 35 patients received EBRT alone to bilateral neck and tumor bed with or without concurrent chemotherapy. 28 patients treated with EBRT to bilateral neck with or without chemotherapy and HDR-BT alone to tumor bed. Both arms received 46-50 Gy to the uninvolved nodal stations with a boost upto 60 Gy to the involved nodal stations by EBRT. The tumor bed in the EBRT alone arm received 60 Gy & tumor bed in the HDR-BT arm received 36-39 Gy in 12-13 fractions by HDR brachytherapy alone. Primary end point was the QOL, which was assessed by EORTC Quality of Life Head and Neck Module (QLQ H&N35) in both arms. Local recurrence (LR) and overall survival (OS) were assessed as secondary end points. Results Of 63 patients, 24 patients in EBRT group and 18 patients in EBRT+HDR-BT group were analyzed at a median follow-up of 37 and 35 months respectively. The overall treatment time in EBRT+HDR-BT was upto 85 days (median 52.5 days) and EBRT group was upto 60 days (median 41 days). The QOL scores were: pain (7.4 vs 11.11), swallowing (33.33 vs 70.83), sensation of taste/smell (16.66 vs 25), speech (5.55 vs 6.94), social contact (12.96 vs 31.94) and social eating (33.33 vs 70.83) in the EBRT+HDR-BT and EBRT only group respectively. Among the head and neck single parameters, observed scores were dry mouth and sticky saliva (33.3 vs 40.28), loosening of teeth (11.11 vs 16.66), skin changes (1.85 vs 9.72), difficult mouth opening (11.11 vs 18.05), need for nutrition supplements (11.11 vs 22.22) and weight loss (3.70 vs 40.27) in EBRT+HDR-BT and EBRT only group respectively. Except weight loss (p value 0.01), none of other parameters attained statistical significance. There is no significant difference in OS (p=.55) and occurrence of LR (p =.93) between the two arms. Conclusion This study proves that by delivering radical dose by brachytherapy to the primary tumor bed improves the QOL in patients with carcinoma tongue without any significant difference in locoregional recurrence. The studies related to quality of life in head and neck cancer treated with brachytherapy in the literature are not subsite specific. This study is specific to oral tongue cancers. Proffered Papers: Highlights of Proffered Papers - Best papers

OC-0508 Molecular classification of endometrial cancer is predictive of response to adjuvant radiotherapy