Abstract Book

ESTRO 37

S581

Poster: Radiobiology track: Normal tissue biology of the lung

tumors developed within 10 days while the CT26 cells did not grew at all (52 days follow up). The specific resistance to tumor growth was proven to be immune response dependent. Transfer of spleen lymphocytes from CT26 bearing mice, cured by DaRT + immuno- modulating agents, protected naïve mice from the growth of CT26 cells. Conclusion Our alpha radiation based brachytherapy provides an efficient method for treatment of solid tumors by alpha radiation and also provides systemic activation of specific anti-tumor immunity. This combined treatment modality holds significant potential for the treatment of non- resectable human cancers PO-1034 High-dose-rate brachytherapy in the treatment of non-melanoma skin cancer. M.A. González Ruiz 1 , J. Quirós Rivero 1 , M.C. Cruz Muñoz 1 , J.J. Cabrera Rodríguez 1 , J.L. Muñoz García 1 , Y. Ríos Kavadoy 1 , M.F. Ropero Carmona 1 , A. Corbacho Campos 1 , F. García Urra 1 1 Infanta Cristina Hospital, Radiation Oncology Department, Badajoz, Spain Purpose or Objective To analyze the results in terms of overall survival (OS), cancer specific survival (CSS), local control (LC), cosmesis and toxicity in patients (pts) with non-melanoma skin cancer (NMSC) treated with high-dose-rate brachytherapy (HDR-BT) treatment, plesiotherapy modality; with radical or adjuvant intention in our hospital. Material and Methods Prospective study of 194 pts with 246 NMSC lesions, T1 (78.9%) and T2 (21.1%) stage treated from May 2015 to May 2017. HDR-BT treatment (6 Gy/fraction; total dose 42 Gy) was used in 88.2% pts with an equivalent 2 Gy dose (EQD2) of 56 Gy. Median total dose of HDR-BT was 42.6 Gy (range 36-50). All the lesions were limited 3-4 mm depth. The median age of the pts was 79 years-old (range 29-97); 61.4% males and 38.6% females. Basal-cell carcinoma (85.8%) was the most frequent histological type and most of lesions were T1 stage (78.9%). The 39.1% of the lesions were treated with Valencia applicators and 42.7% with custom-made moulds. Results The median follow-up was 20 months (range 2-61). The OS, CSS and LC was 94.7%, 100% and 95.1% respectively. There were no differences in terms of LC related with the type of applicator used (p 0.910) and with the T stage (p 0.149). The majority of pts had acute skin toxicity grade 1-2. Conjunctival toxicity appeared in 8.9 % of the pts. Cosmetic results were considered as excellent/very good in all patients. Conclusion Despite of the short follow-up, plesiotherapy treatment is a good alternative treatment which provides excellent results for local control and cosmesis (similar to the main studies) furthermore facilitates treatment compliance that is very relevant in elderly patients. HDR brachytherapy is a safe and attractive treatment option for non-surgical pts or when the cosmetic results are no good after surgery.

PO-1035 Detection of radiation induced lung fibrosis using x-ray dark-field imaging in a murine model T. Gora 1 , R. Burkhardt 1,2 , S. Umkehrer 3 , J. Herzen 3 , D. Schilling 1,2 , A. Feuchtinger 4 , A.K. Walch 4 , T.E. Schmid 1,2 , G. Multhoff 1,2 , P.B. Noël 5 , E.J. Rummeny 5 , F. Pfeiffer 3,5,6 , S.E. Combs 1,2 , J.J. Wilkens 1 1 Klinikum rechts der Isar- Technical University of Munich, Department of Radiation Oncology, Munich, Germany 2 Helmholtz Zentrum München, Institute of Innovative Radiotherapy iRT, Neuherberg, Germany 3 Technical University of Munich, Chair of Biomedical Physics- Department of Physics and Munich School of BioEngineering, Garching, Germany 4 Helmholtz Zentrum München, Abteilung Analytische Pathologie, Neuherberg, Germany 5 Klinikum rechts der Isar- Technical University of Munich, Department of Diagnostic and Interventional Radiology, Munich, Germany 6 Technical University of Munich, Institute for Advanced Study, Garching, Germany Purpose or Objective Radiation induced lung fibrosis is a common side effect of radiation therapy and limits the radiation dose that can be applied to treat thoracic tumours. Lung fibrosis leads to an irreversible destruction of the lung, chronic respiratory insufficiency and sometimes death. Usually CT or planar x-rays are employed to detect lung fibrosis; however, these methods are not very sensitive and the differentiation between fibrosis and an early stage of inflammation is difficult. The aim of this study is to test new x-ray dark-field imaging methods to detect radiation induced lung fibrosis in a murine model, and to investigate the influence of different irradiated lung volumes. These insights can help to detect lung fibrosis at an early stage and to optimize treatment planning for humans. Material and Methods 24 C57BL/6 mice were subdivided into four groups to be treated with different irradiation settings: full right lung, upper right lung lobe, lower right lung lobe, all irradiated with 20 Gy in a single fraction, and a control group, which was not irradiated. Local irradiation was performed with 220 kV x-rays using the Small Animal Radiation Research Platform (SARRP, Xstrahl Ltd, UK). Two opposing anterior and posterior oblique fields were used to avoid the heart. Immediately before irradiation and afterwards in regular intervals of four weeks, the mice were imaged for eight months using the novel preclinical imaging device SkyScan 1190 (Bruker, Belgium). It uses x-ray dark-field imaging for both, projection images and CT, and also provides a conventional absorption image (projection and CT), which is later used for comparison. Results First structural changes within the treated area could already be seen 8-12 weeks after irradiation, in most irradiated mice after 20 weeks. These changes increased with time and are clearly visible in the dark-field images. A clear volume effect could be observed, both in terms of severity of the change in lung tissue and in the time of its onset. Therefore, the benefit of dark-field imaging compared to conventional absorption images is apparent both in a qualitative, visual evaluation and in a quantitative evaluation based on the image grey values in