ESTRO 38 Abstract book

S131 ESTRO 38

evaluate the combined action of several BFCs in combination with chemotherapy and radiotherapy in PDAC models and to identify mechanisms involved in chemo / radiosensitization at the cellular and molecular levels Material and Methods Cell survival was evaluated in vitro in the presence of BFCs in combination on 4 pancreatic tumor cell lines. The production of reactive oxygen species (ROS) was measured by flow cytometry and fluorescence microscopy. Molecular mechanisms have been decrypted by western blot (signaling pathways) and flow cytometry (cell cycle and apoptosis). Finally, we evaluated the association of BFCs in gavage with intraperitoneal gemcitabine chemotherapy and with radiotherapy (2 Gy/fraction) in vivo , on subcutaneous CAPAN-2 cell xenografts. Results In vitro , resveratrol (R), capsaicin (C) and sulforaphane (S) were cytotoxic with significantly higher inhibitory effect in combination (R + C), (C + S) or (R + C + S), without effect on fibroblasts. In addition, the combinations potentiated the otherwise limited action of gemcitabine on cells tested in vitro . In vivo , the addition of R + C to treatment with gemcitabine at reduced dose allowed tumor inhibition equivalent to that obtained with gemcitabine at full dose. Furthermore, in vitro , the addition of BFCs alone and in combination with radiotherapy significantly increases cellular toxicity on the CAPAN-2 epithelial line, compared to radiotherapy alone and BFCs alone or combined. In vivo , the combination R + C associated with radiotherapy allowed a significant decrease in tumor volumes compared to radiotherapy alone. The study of signaling pathways showed an increase of pro-apoptotic proteins with the association R + C and radiotherapy, in relation with an increased induction of ROS, but also, surprisingly, an inhibition of the repair of the DNA by inhibition of ATM phosphorylation. These two combined effects precipitated the death of the tumor cells. Conclusion Combinations of R + C have a chemosensitizing and radiosensitizing effect in a preclinical model of PDAC, with identified molecular mechanisms relevant in the context of the therapies tested. By combining BFCs with radiochemotherapy with gemcitabine, we can hope for a double potentiation of radiotherapy and chemotherapy, by increasing the effectiveness of RT, and by reducing the dose of gemcitabine associated for similar efficiency and better tolerance treatment. OC-0267 Imaging the effect of Atovaquone on the hypoxia-related marker CAIX in head and neck cancer models F. Huizing 1 , B.A. Hoeben 1 , O.C. Boerman 2 , S. Heskamp 2 , J. Bussink 1 1 UMC St Radboud Nijmegen, Radiation oncology, Nijmegen, The Netherlands ; 2 UMC St Radboud Nijmegen, Nuclear Medicine, Nijmegen, The Netherlands Purpose or Objective Tumor hypoxia is an important cause of radio resistance and is associated with poor patient outcome. Therefore, methods to reduce hypoxia before or during radiotherapy are of great value. The drug Atovaquone shows great potential in this prospect. By reducing the oxygen consumption rate of cells it has been shown to reduce hypoxia both in vitro and in vivo. Recently, the radioactive tracer 111 In-girentuximab- F(ab’) 2 was developed for imaging of the hypoxia related marker Carbonic Anhydrase IX (CAIX). Successful imaging of the hypoxia reducing effect of Atovaquone could help predict the effectiveness of radiotherapy. Aim of this study is to assess the effect of Atovaquone on tumor hypoxia with the use of the SPECT tracer 111 In- girentuximab-F(ab’) 2 . Material and Methods

Athymic mice with subcutaneous FaDU or SCCNij202 head and neck carcinoma xenografts were treated with Atovaquone (50mg/kg) during 8 days or were held for 48 hours in a hypoxic chamber (8% O 2 ). After treatment mice were injected with 111 In-girentuximab-F(ab’) 2 and 24 hours after injection the mice were imaged using a microSPECT/CT. Tracer uptake was also measured by analyzing ex vivo radioactivity counting and autoradiography of the tumor sections. Immunohistochemical staining was used to determine CAIX expression and hypoxia. Results Atovaquone treatment decreased both CAIX expression and hypoxia staining by 54 ± 33% and 50 ± 21% in the FaDu tumor model, while in the SCCNij202 no difference was observed. Treatment with hypoxic breathing did not increase CAIX expression or hypoxia staining in both tumor models. 111 In-girentuximab-F(ab’) 2 tumor uptake was generally in line with CAIX expression, however mice treated with hypoxic breathing showed an increased amount of necrosis and a decreased amount of tumor tracer uptake. Conclusion Atovaquone decreases tumor hypoxia in the FaDu tumor model, but not in the SCCNij202 model. 111 In- girentuximab-F(ab’) 2 specifically targets to CAIX- expressing areas in head and neck cancer xenografts. The radiotracer has potential for therapy monitoring, but differences in tumor perfusion and necrosis can hamper accurate quantification. OC-0268 Intrinsic radiosensitivity, genomic-adjusted radiation dose and patterns of failure of penile cancer P. Johnstone 1 , G.D. Grass 1 , M. Azizi 2 , K. Ahmed 1 , G.S.J. Yoder 3 , E. Welsh 4 , W. Fulp 4 , J. Dhillon 5 , J. Torres-Roca 1 , A. Giuliano 6 , Z. Yuan 1 , P. Spiess 2 1 Moffitt Cancer Center, Radiation Oncology, Tampa, United States Minor Outlying Island ; 2 Moffitt Cancer Center, Urology, Tampa, United States Minor Outlying Island ; 3 Moffitt Cancer Center, Genomics Core, Tampa, United States Minor Outlying Island ; 4 Moffitt Cancer Center, Biostatistics and Bioinformatics, Tampa, United States Minor Outlying Island ; 5 Moffitt Cancer Center, Anatomic Pathology, Tampa, United States Minor Outlying Island ; 6 Moffitt Cancer Center, Cancer Epidemiology, Tampa, United States Minor Outlying Island Purpose or Objective Our group previously developed algorithms to characterize a genome-based radiosensitivity index (RSI) and a clinically actionable model to calculate genomic-adjusted radiation dose (GARD), which have been validated in various clinical cohorts. Herein, we characterized the RSI and GARD profiles in a cohort of patients with penile squamous cell carcinoma (PeSCC). We further assessed the potential correlation of GARD with the clinical outcomes in PeSCC patients treated with postoperative radiation therapy (PORT). Material and Methods A total of 25 PeSCC samples were identified from our institution's tissue bank to analyze RSI. Fresh frozen PeSCC tissue samples were analyzed using Affymetrix U133 2.0 microarray chips. RSI score (range 0–1.0) was derived for each sample using the previously published algorithm for a specific 10 genes signature. The comparison of RSI among PeSCC and various selected epithelial cancers were assessed. GARD values were calculated as described in our prior studies using a postoperative RT dose of 50 Gy. A cohort of 18 patients treated with PORT was reviewed for clinical correlation. Results The median RSI for the tissue cohort was 0.475 (range 0.215-0.682). The majority of the lesions (n=21; 84%) are radioresistant using a previously reported RSI cut-point of