ESTRO 2020 Abstract book

S539 ESTRO 2020

2 N Engl J Med. 2018 Jan 25;378(4):331-344. doi: 10.1056/NEJMoa1708984. 3 Blood. 2016 May 5;127(18):2189-92 4 Blood. 2004 Dec 1;104(12):3483-9. Epub 2004 Aug 17. 5 Int J Radiat Oncol Biol Phys. 2010 Mar 1;76(3 Suppl):S70- 6

Conclusion In selected patients with diffuse cutaneous lymphoma and extensive head involvement, the treatment of total scalp and face irradiation with TomoTherapy technique is feasible and effective with low toxicity. PO-0924 Impact of radiation techniques on lung toxicity in patients with mediastinal Hodgkin lymphoma N.B. Pepper 1 , M. Oertel 1 , C. Kittel 1 , K.J. Kröger 1 , U. Haverkamp 1 , H.T. Eich 1 1 University Hospital Muenster, Department of Radiation Oncology, Muenster, Germany Purpose or Objective Modern treatment strategies for Hodgkin lymphoma see a shift from extended-field radiotherapy (RT) to reduced volumes such as involved-field (IF) or involved-site RT, achieving excellent results with combined modality treatment [1]. Consequently, the reduction of long-term toxicity and secondary neoplasia has gained pivotal importance. Mediastinal RT, especially when combined with bleomycin, may result in substantial pulmonary morbidity and mortality [2-4]. Anyhow, the question of whether the use of modern RT techniques like IMRT is superior to standard APPA regarding lung toxicity remains unanswered and is addressed by the hereby presented analysis. Material and Methods This study evaluated 27 patients who underwent RT for Hodgkin lymphoma in our institution between 2009 and 2013. For each of them, three different treatment plans for a 30 Gy IFRT were created (APPA, 5-field-IMRT and 7- field IMRT). These plans were analyzed concerning their inherent „normal tissue complication probability“(NTCP) concerning radiation pneumonitis and secondary pulmonary malignancies using parameters published by Burman and QUANTEC [5]. In each case, the determined values of the treatment plan used were correlated to the follow-up of the patient. Results The comparison of different radiation techniques showed a significant difference in favor of standard APPA (p<0.01). The determined risks of lung toxicity were significantly higher in plans using 7-field-IMRT than in plans using 5- field-IMRT. The absolute juxtaposition showed an increase in risk for radiation pneumonitis of 1% for plans using 5- field-IMRT over APPA according to QUANTEC-parameters (Burman: 0.15%) and 2.6% when using 7-field-IMRT over APPA (Burman: 0.7%) as well as 1.6%, when using 7-field- IMRT over 5-field IMRT (Burman: 0.6%). The mean risk for pulmonary secondary malignancies was 0.1% higher in plans using 5-field-IMRT than APPA and 0.19% higher in plans using 7-field-IMRT than APPA as well as 0.09% higher in plans using 7-field-IMRT than 5-field-IMRT. Only one of 27 patients showed signs of radiation induced pneumonitis during follow-up. No secondary pulmonary malignancies were detected. Conclusion Radiation-induced lung toxicity is rare after treatment for Hodgkin lymphoma, but may be influenced significantly by the RT technique used. In this study, APPA RT-plans demonstrated a decrease in potential radiation pneumonitis and pulmonary malignancies. However, this advantage has to be carefully weighted against dose exposure to other organs such as the heart and the mammary glands. Biological planning using NTCP may have the potential to define personalized RT strategies. References 1 Int J Radiat Oncol Biol Phys. 2014 Jul 15;89(4):854-62.

Poster: Clinical track: Breast

PO-0925 Internal Mammary Lymph Node Volumes: What Radiation dose is received with modified wide tangents? R. Ujaimi 1 , M. Attar 1 , N. Awad 2 , Z. Hasan 3 , S. Al- Khateeb 4 , N. Abbas 4 , W. Baageel 4 , S. Khayyat 4 1 Faculty of Medicine - King Abdulaziz University, Radiotherapy section- department of Radiology, Jeddah, Saudi Arabia ; 2 King Abdulaziz University Hospital, Radiotherapy section- department of Radiology, Jeddah, Saudi Arabia ; 3 King Faisal Specialist Hospital and Research Center, Biomedical Physics, Jeddah, Saudi Arabia ; 4 Faculty of applied medical Sciences - King Abdulaziz University, Diagnostic radiography technology, Jeddah, Saudi Arabia Purpose or Objective There is a growing interest in radiating the internal mammary nodes (IM) in the context of adjuvant radiotherapy in breast cancer. There has been variation in defining its CTV and the acceptable coverage. Clear definition is necessary particularly when using modified treatment techniques. This paper ought to estimate the dose delivered to an institutionally defined IM CTV using the standard modified wide tangent technique (MWT). Material and Methods Ten patients were randomly selected. The IM vessels in the first three intercostal spaces were contoured. Five mm were added, and trimmed from anatomical boundaries, to create CTV. Subsequently, three PTVs were created .PTV1 was created by adding 5 mm uniform expansion around CTV. To create PTV2, PTV 1 was trimmed from the lung and heart. PTV 3 was created by expanding 5 mm around the IM vessels. A plan optimization target volume was generated by adding 1 cm around the vessels following the MA 20 protocol for CT based planning. Apart from the later volume, the planner was blinded to all other volumes. . The treatment planning was forward using 3-4 fields with the aim to cover the target volumes by 90% to 95% of the dose whilst keeping V20 of the lung below 35% and the V25 of the heart below 10% with as minimum mean heart dose as possible . Two modified wide tangential fields were used to cover the internal mammary lymph nodes and breast or chest wall and one anterior field, with or without a posterior field for the supraclavicular lymph nodes. A dose of 50Gy/25 fractions was prescribed at the isocenter. The heart and lungs were contoured using RTOG consensus guidelines. DVH curves for normal tissue were generated. Results Six left and four right sided patients were included. Nine and one patients underwent mastectomy and lumpectomy, respectively. The mean percentage of the volume that received 95% (V95) ±SD was: IM vessel (V95) = 85.491 ±14.059, CTV (V95) = 78.727 ±14.289, PTV 1 (V95) = 65.879 ±11.987, PTV 2 (V95) = 76.047 ±12.311, PTV 3 (V95) = 70 ±12.836. The mean percentage of the volume that received 90% (V90) ±SD were: IM vessel (V 90) = 91.866±10.867, CTV (V90) = 86.038 ±12.788, PTV 1 (V90) = 75.341 ±11.553, PTV 2 (V90) = 81.246% ±11.609, PTV 3 (V90) = 81.312 ±11.697. The mean heart V25 was 0.037±0.04 and 5.5±3.4 for right and left sided patients, respectively. The mean of the mean heart dose for the left sided patients was 4.5± 1.8 .The mean lung V20 was 35.148±0.39 and 34.314±1.17 for right and left sided patients, respectively.