ESTRO 36 Abstract Book

S523 ESTRO 36 2017 _______________________________________________________________________________________________

(PDAC). Microscopically incomplete resection (R1) is often associated with early local recurrence (LR) and, therefore, represents a negative prognostic factor. The aim of this study was to analyze the total PDAC proteome of patients who received radiochemotherapy (RCT) following incomplete resection in order to identify proteins associated with post-RCT LR. Material and Methods Thee patients with early LR (median 6 months after resection, range 5 to 10 months) and three patients with late LR (median 18 months after resection, range 13 to 27 months) were identified from our clinical database. Formalin fixed paraffin-embedded tissue obtained from surgical PDAC specimens was used for proteome analysis. After micro-dissection, tissue was de-paraffinized and rehydrated, followed by protein extraction and trypsin digestion. The samples were analyzed by tandem mass spectrometry. To identify significantly up- or down- regulated proteins, linear models for microarray data (LIMMA) were applied; the p-value was set to 0.01. Results Patients received a median RT total dose of 50.4Gy and concurrent chemotherapy with two courses of 5-FU. Overall survival was reduced in patients with early LR as compared to patients with late LR (7 vs. 30 months, p=0.0001). A total of 1,878 proteins were quantified in both cohorts with 1,656 proteins quantified in the early LR group and 1,769 quantified in the late LR group. LIMMA method identified 18 proteins significantly up- or down- regulated. 7 proteins were up-regulated in the early LR group such as MAOA, ALDH1A1, creatine kinase B and mucin-5AC being involved in tumorigenesis. 11 proteins were up-regulated in the late LR group including fascin, integrin beta-4, histidine rich glycoprotein and CDC42. Further analysis demonstrated the early LR group to exhibit an exocrine-like phenotype including expression of pancreatic proteins absent in the late LR group. 13 exocrine-related proteins were identified such as carboxypeptidase B and chymotrypsin-C. Conclusion Analyzing proteomic data of PDAC patients undergoing post-operative RCT after R1-resection, proteomic expression profiles associated with early vs. late post-RCT LR were identified. These proteomic biomarkers may serve to stratify patients according to prognosis in future trials and to assess a potential benefit of post-operative RCT. PO-0954 A model to study long-term impact of radiation towards the colorectal area F. Sjöberg 1 , D. Malipatlolla 1 , G. Steineck 1 , C. Bull 1 1 The Division of Clinical Cancer Epidemiology, Department of Oncology- University of Gothenburg, Gothenburg, Sweden Purpose or Objective A deeper understanding of the radiophysiology following radiotherapy is imperative. With a few exceptions, rodent models of high-dose gastrointestinal radiation injury typically cause lethality within 5-8 days, limiting the possibility to study the progression of injury over time. We have developed a model that allows for delivering radiation in fractions at high doses, while maintaining excellent survival. Material and Methods Adult male C57/BL6 mice placed in a silicone mold were exposed to rectal irradiation using a linear accelerator (Varian Clinac 600 CD), the field limited to 1,5 cm of the distal part of the colon. Each mouse received 6 or 8 Gy, twice daily in 12 hours intervals, in 2, 3 or 4 fractions total. Acute cell apoptosis was examined, and histological changes at six weeks post-irradiation. Results Irradiation caused apoptosis at 4.5 hours, mainly limited to the distal colon. At six weeks post-irradiation, crypts

displayed overt signs of radiation-induced degeneration, as has been described in human irradiated intestinal tissue. The number of degenerated crypts was heavily increased at the fourth fraction, regardless of dose. The number of macrophages, indicating inflammation, was likewise apparent after the fourth fraction. Crypt damage was restricted to individual crypts, nearby crypts were unaffected with regards to cell production and survival. Angiogenesis was induced, likely as a compensatory mechanism for hypoxia. Conclusion Our model is suitable to study late gastrointestinal injury induced by high-dose fractionated radiation. The placement of the radiation field makes the model especially convenient for testing interventions that can be delivered rectally. PO-0955 Co-treatment of MSC and vascular permeability inhibitor reduces radiation side effects on the colon V. Monceau 1 , C. Demarquay 1 , A. Accarie 1 , L. Moussa 1 , B. Doix 1 , M. Benderitter 1 , A. Sémont 1 , N. Mathieu 1 1 Institut de Radioprotection et de Sûreté Nucléaire IRSN, PRP-HOM- SRBE- LR2I, Fontenay aux roses, France Purpose or Objective The efficacy of radiotherapy requires an optimal compromise between tumor control and normal tissue injury. Non-neoplastic tissues around abdomino-pelvic tumor can be damaged by ionizing radiation leading to acute and/or chronic gastrointestinal complications which affect quality of life with substantial morbidity and mortality. There is no unified approach to the assessment and the treatment of radiotherapy delayed side effects, characterized mainly by uncontrolled inflammation and tissue fibrosis. We previously demonstrated that mesenchymal stromal cells (MSC) treatment improves colonic regeneration and reduces partially the ulcer size by the margins (Sémont, 2013). Moreover, studies showed that the vascular compartment is improved after MSC treatment and could play a key role in the inflammatory process and the epithelial regeneration. However, these aspects have not yet been investigated after irradiation. In this study, we investigate the effect of MSC treatment on vascular compartment. We analyze the angiogenesis process, progenitor’s recruitment in blood and associated chemoattractant molecules secretion as well as vascular permeability. The aim of this study is to determine a new way to improve MSC treatment. Material and Methods We generated, in SD rat, colonic radiation-induced lesions similar of those seen in patients suffering of late side effects after pelvic radiotherapy (29Gy). Three weeks after irradiation (established damages) 5.10 6 of MSC from fat tissue were injected intravenously (IV). Results The first results showed that MSC treatment increase the amount of blood vessels. This process is associated with an increase of the growth factor VEGF, but also a recruitment of endothelial progenitor cells, two events necessary for the neo-vascularization. We also demonstrated that MSC treatment ameliorates the quality of blood vessels (the number of fully muscularized capillaries was reduced in ulcer and border areas). However, MSC treatment has no effect on the vascular permeability nor the number of inflammatory cells. Therefore, we realized MSC injections concomitantly with an inhibitor of vascular permeability which was iteratively infused intravenously. We demonstrated that the co- treatment reduces considerably the size of the ulcer comparatively with only MSC treatment suggesting that the beneficial effects of MSC were potentiated with an inhibitor of vascular permeability. Conclusion