ESTRO 36 Abstract Book

S541 ESTRO 36 2017 _______________________________________________________________________________________________

Neoadjuvant radiotherapy (NeoRT) improves tumor local control and facilitates tumor resection in many cancers. The timing between the end of the NeoRT and surgery is driven by the occurrence of side effects or the tumor downsizing. Some clinical studies demonstrated that the timing of surgery and the RT schedule influence tumor dissemination and subsequently patient overall survival. Previously, we developed a pre-clinical model demonstrating an impact of NeoRT schedule and the timing of surgery on metastatic spreading (Leroi et al. Oncotarget 2015). Here, we evaluate the impact of NeoRT on the tumor microenvironment by functional MRI (fMRI). We aim to identify non-invasive markers allowing to determine the best timing to perform surgery and avoiding tumor spreading. Material and Methods Based on our NeoRT model, MDA-MB 231 and 4T1 cells were implanted in the flank of SCID and BalbC mice, respectively. We locally irradiated tumors with 2x5Gy and then surgically removed at different time points after RT. Diffusion Weighted (DW) -MRI was performed every 2 days between RT and surgery. For each tumors we acquired 8 slices of 1 mm thickness and 0.5 mm gap with an 'in plane voxel resolution” of 0.5 mm. For DW-MRI, we performed FSEMS (Fast Spin Echo MultiSlice) sequences, with 9 different B-value (from 40 to 1000) and B0, in the 3 main directions. We performed IVIM (IntraVoxel Incoherent Motion) analysis to obtain information on intravascular diffusion, related to perfusion (F: perfusion factor) and subsequently tumor vessels perfusion. Results With the MDA-MB 231, we observed a significant peak of F at day 6 after irradiation, this increasing is about 60% of the basal value (n=6, p<0,05). Moreover, D* parameters (also related to perfusion) increase at the same time. The other parameters of the DW-MRI, ADC and D presented no modification. We observed similar results with 4T1 cells, where F increased at day 3 (about 55%, n=10, p<0,05) then returned to initial level. The difference in timing for the peak of F (day 6 vs day 3) could be related to the difference in tumor growth according to the cell line (four weeks for MDA-MB 231 cells vs one week for 4T1cells). We performed surgery at the time of the F parameter peak in the MDA-MB 231 and we observed a decrease of the metastasic burden compared to surgery performed at day 4 or day 11(absolute number of metastasis 23 VS 1 VS 8 For the first time, we demonstrate the feasibility of repetitive fMRI imaging in preclinical models after NeoRT. With these models, we show a significant difference in perfusion-related parameters (D* and F) at a specific time point depending of the tumor cells. These modifications are correlated to a decrease of metastasis spreading related to the surgery procedure. These results open new perspectives in the personalized medicine and MRI guided surgery timing after NeoRT. PO-0989 Sub-lethal radiation allows an efficient antitumor therapy with engineered T-cells in RIP-Tag2 mice F. Maione 1 , E. Garibaldi 2 , X. Zhuang 3 , J. Robinson 3 , R. Bicknell 3 , E. Delmastro 2 , A. Miranti 4 , S.P. Lee 3 , P. Gabriele 2 , E. Giraudo 1 1 Candiolo Cancer Institute- Torino- Italy, Department of Science and Drug Technology, Candiolo TO, Italy 2 Candiolo Cancer Institute- Torino- Italy, Radiotherapy Unit, Candiolo TO, Italy 3 University of Birmingham, Institute of Immunology and Immunotherapy, Birmingham, United Kingdom 4 Candiolo Cancer Institute- Torino- Italy, Medical Physics Unit, Candiolo TO, Italy with n=4). Conclusion

The important goal of tumor immunotherapy is to identify strategies to modulate in vivo the anti-tumor immunity in order to achieve clinical efficacy. In the last decade great progresses have been made in the field of tumor immunology and an increasing number of tumor antigens have been identified. In particular, several different engineering T-cells were designed to express receptors specific for antigens expressed in the tumor compartment. Herein, in order to block tumor progression, we employed Chimeric Antigen Receptors (CARs) technology to target the tumor vasculature. To this aim we used a spontaneous mouse tumor model of pancreatic neuroendocrine insulinoma, RIP-Tag2. Despite its low frequency in cancer patients, we chose this model, since develops invasive tumors through well-characterized and synchronous pre- malignant stages, sustained by active angiogenesis. Little is known about the effects of ionizing radiation on tumor burden of RIP-Tag2 mice and the impact of whole-body irradiation on the overall survival. Material and Methods In the current study tumor-bearing RIP-Tag2 mice were irradiated with two different sub-lethal dosages (5 and 6 Gy respectively), by means of 6MV x rays of Tomotherapy; a treatment plan was performed and evaluated for each cage pie . We hypothesized that sub-lethal radiation might be more effective than a lethal dose radiation and clinically acceptable in promoting anti-tumor immunity. The day after the irradiation mice were injected with enginered T-cells (20 million cells). Results Firstly,we observed that irradiation per se did not affect tumor growth and all the mice survived until the end of treatment. Furthermore, by means of this approach, we found statistically significant inhibition of tumor growth in mice treated with anti-vasular CAR-T-cells compared with controls. Interestingly, we noticed a strong reduction in tumor vessel area and a decrease of blood vessel permeability. Conclusion These data suggest that the tumor vasculature can be efficiently targeted by specific CAR-T-cells, causing a significant reduction in the tumor burden of RIP-Tag2 mice and potentially in other tumor types. PO-0990 Combining radiotherapy and notch inhibition in melanoma K. Thippu Jayaprakash 1,2 , M. Hussein 3 , A. Nisbet 3,4 , R. Shaffer 2 , M. Ajaz 1,2 1 University of Surrey, Department of Clinical and Experimental Medicine, Guildford, United Kingdom 2 St Luke's Cancer Centre- Royal Surrey County Hospital, Department of Oncology, Guildford, United Kingdom 3 St Luke's Cancer Centre- Royal Surrey County Hospital, Department of Medical Physics, Guildford, United Kingdom 4 University of Surrey, Department of Physics, Guildford, United Kingdom Purpose or Objective Melanoma is classically viewed as a radioresistant tumour. Phenotypic plasticity, specifically the emergence of a cancer stem cell (CSC) population, may be one reason for this. The notch signalling pathway plays a crucial role in maintenance of the CSC phenotype, and also in cell migration. This pathway is frequently aberrant in melanoma and is therefore a potential mechanism for the observed radioresistance. The aims of this project were (1) to investigate whether notch inhibition with the γ - secretase inhibitor, RO4929097 that targets γ - secretase cleavage and thereby inhibiting the notch signalling pathway, improves the radiation sensitivity of melanoma cell lines; (2) to investigate the effects of notch inhibition and radiotherapy on melanoma cell migration. Material and Methods

Purpose or Objective