ESTRO 2020 Abstract Book

S285 ESTRO 2020

cells) are a pluripotent mesenchymal stem cell (MSC) sub- population, easily isolated from bone marrow (BM-Muse) by cell sorting using an embryonic marker (SSEA3). When injected, these cells have the ability to migrate, integrate injured or inflammatory tissues and repair tissues through their immunomodulatory property and differentiation into tissue specific cells(Iseki et al. 2017; Kuroda et al. 2013). My project consists in the use of cell therapy using injection of Muse cells to reduce or prevent the development of RIPF. I use a well established mouse (C57BL/6J) model of RIPF(Sharplin et al. 1989; Jackso et al. 2010) to determine if intravenous injection of Muse cells (10 000- 60 000 BM-Muse) at 2h or 24h or 2 weeks after thoracic irradiation (14Gy X-Rad) reduce the development of fibrosis. Mice are followed during 20 weeks by Computed Tomography and survival. Then the animals are sacrificed and fibrosis is confirmed by histologic analysis of HES on lung sections. Our results showed that the 20-50% of irradiated non injected mice started to die 12 weeks irradiation and at 20 weeks the survival was 20-25%. In the group of mice treated with Muse (10 000- 30 000) 2h post RT, we observed survival of 100% of mice. CBCT and HES analysis showed that the 30 000 Muse cells prevent the development of fibrosis whereas 10 000 of Muse cells are not efficient to prevent the fibrosis but we observed a delay of RIPF development. In contrast when the mice were injected 24h or 2 weeks post RT, independent on the number of injected cells, we observed an improve of survival but all mice developed fibrosis.These experiments showed that Muse cells are able to prevent the development of RIPF without compromise the mice survival when injected early after irradiation. The perspective of this work is: To find new markers of Muse cells. To date, only the SSEA-3 marker discriminate the Muse cells from other MSC. A proteomic analysis is ongoing to find new markers characterizing Muse cells associated with their capacities of immunomodulation, differentiation and repair. This experiment will be performed on sorted Muse SSEA3 + and MSC negatives for SSEA3. To monitor in vivo the migration and localization of Muse cells soon after injection . The higher therapeutic potential of Muse cells compared to MSC is their integration at long term into the injured tissue wich seems to ease tissue reparation. Cells will be transfected with a luciferase plasmid that expressed luciferase with a high sensitivity and localization of muse cells in the lung will be monitored by bioluminescence in vivo . The precise localization of Muse cells will be confirmed by immunofluorescence on lung section using a specific anti-human HLA antibody. To investigate the role of Muse cells on inflammatory process and the modulation of immune response. After irradiation early tissue response include rapid production of pro-inflammatory cytokines (IL-3, IL-6, IL-7, TGFb, TNFa) promoting infiltration and activation of immune cells (neutrophils, macrophages). The late phase (from 12 weeks) is characterized by chronic inflammation and the accumulation of cells in the lung parenchyma such as lymphocytes, macrophages and myofibroblasts secreting extracellular matrix leading to RIPF (4 months to years)(Wynn 2011; Chen et al. 2018). Thus, we will analyze the modification of immune system response focusing on lymphocytes Th1/Th2 and macrophages (M1/M2), and the different changes occurring in lung parenchyma such as endothelial and epithelial apoptosis, myofibroblasts accumulation and

collagen deposition. For that, we will perform immune cells analysis by flow cytometry, western blot and immunohistochemistry to analyze modifications in lung parenchyma, and Sirius red to quantify collagen deposition. Cytokines secretion will be assessed using cytokine array focusing mainly on TGFband Th2 cytokine signatures known to mediate pro-fibrotic effects. All those experiments will be done at short (3, 7, 15, 30 days) and late (12, 20 weeks) times after irradiation in both lung interstitium lysats and broncho-alveolal lavages and on lung sections for histological analysis from irradiated mice injected or not with Muse cells. PH-0521 Paravertebral Muscle Training in Patients with Unstable Spinal Metastases T. Sprave 1 1 Universitaetsklinik Freiburg, RadioOncology, Freiburg, Germany Purpose or Objective Isometric paravertebral muscle training (IPMT) may improve mobility, pain, and quality of life (QOL) in cancer patients with spinal metastases. However, this regimen remains unproven in patients with unstable spinal metastases (USM), a population at high risk for clinical exacerbation with such interventions. Thus, we conducted this exploratory, non-blinded, randomized controlled trial (NCT02847754) to evaluate the safety/feasibility of IPMT and secondarily assess pain, bone density, pathologic All patients had histologically/radiologically confirmed USM (per Taneichi score) and underwent non-operative management with 5-10 fractions of palliative radiotherapy (RT). Randomization (1:1) groups were IPMT (intervention, INT) or muscle relaxation (control, CON); both lasted 15 minutes/day and started concurrently with radiotherapy. The primary endpoint was feasibility (completion of training programs 3 months post-RT). Secondary endpoints were pain response (Visual Analog Scale) and opioid consumption, bone density and pathologic fracture rate, and QOL (EORTC questionnaires). Results Sixty patients were randomized and 56 received protocol therapy. Mean survival in both groups was 4.4 months. There were no adverse events with either training regimen. Altogether, ≥80% of the planned sessions were completed by 55% (n=16/29) in CON and 67% (n=18/27) in INT. Regarding the post-radiotherapy home-based training, ≥80% of planned sessions were completed by 64% (n=9/14) of the INT cohort. There were no differences in pain scores, opioid consumption, or bone density between arms (p>0.05 for all). No difference was observed between groups regarding new pathological fractures (INT: n=1 vs CON: n=3) after 3 months (p=0.419).There were no QOL differences between arms (all parameters p>0.05). Conclusion IPMT is safe and feasible for high-risk USM patients. Future trials adequately powered for relevant endpoints are thus recommended. PH-0522 Fractionation and early mortality in palliative radiotherapy across the English NHS K. Spencer 1 , P. Hall 2 , A. Henry 3 , G. Velikova 3 , S. Whalley 4 , R. Birch 4 , K. Le Calvez 5 , M. Williams 6 , E. Morris 4 1 University of Leeds, Leeds Institute of Health Sciences, fracture rate, and QOL. Material and Methods Poster Highlights: Poster highlights 17 CL : Palliation