ESTRO 2021 Abstract Book

S1640

ESTRO 2021

positive group had a higher hypoxic fraction (P=4×10 -5 ), higher Ki67-positive cell fraction (P=3×10 -4 ), and spatial co- localization of Ki67-positive cells and hypoxia for most biopsies. GSEA of genes upregulated in this group corroborated a proliferative phenotype, with enrichment of hallmarks related to proliferation (FDR q-value < 10 -12 ). For the negative and non-significant group, no co-localization between Ki67-positive cells and hypoxia was seen, and GSEA revealed enrichment of hallmarks related to immune responses (FDR q-value < 0.06). A higher prevalence of high Gleason grades was found for the positive group (>= 3, P=0.004). Conclusion Hypoxia-related histological features analyzed by digital pathology enable classification of prostate cancer into two groups with different phenotypical and clinical characteristics; one group with high proliferation and high Gleason grade and another group with immune responses and lower Gleason grade. The spatial co-localization of proliferation and hypoxia in the former group indicates a high tolerance to hypoxia. PO-1923 Exosomes in postoperative wound microenvironment of patients with breast cancer treated with IORT K. Kulcenty 1,3 , M. Lach 1 , I. Piotrowski 2,3 , W. Suchorska 1,4 1 Greater Poland Cancer Centre, Radiobiology Lab, Department of Medical Physics, Poznań, Poland; 2 Greater Poland Cancer Centre, Radiobiology Lab, Department of MEdical Physics, Poznań, Poland; 3 University of Medical Sciences, Department of Electroradiology, Poznań, Poland; 4 University of Medical Sciences, Department of Electroradiology, Poznań, Poland Purpose or Objective The induction of wound healing response is believed to be one of the reasons of local relapse in breast cancer (BC) patients. In normal tissue, it is necessary for tissue repair. However, induction of adaptive and innate immune response in tumor tissue stimulates cell survival, induction of angiogenesis and extravasation of circulating tumor cells. Previous studies have shown that surgical wound fluids (SWF) obtained from BC patients after the breast conserving surgery (BCS) stimulated motility and invasiveness of tumor cells in vitro. Moreover we have demonstrated that intraoperative radiation therapy (IORT) significantly inhibits the stimulatory effect of SWF on tumor cells in vitro. This effect may be due to both direct cell killing by ionizing radiation and by modulating the tumor microenvironment. Nowadays exosomes are believed to be the most important molecules responsible for cell to cell contact and mediate the changes of tumor microenvironment connected to further tumor progression and therapy resistance. We speculate that one of the key components of SWF which distinguish BC cells response to BCS and IORT group of SWF are exosomes. Thus the main aim of this study was to isolate and analyze the exosomes from BCS and IORT patients. Materials and Methods SWF were isolated from BC patients after BCS and BCS followed by IORT. At least 20 SWF were pooled and exosomes were isolated using ultracentrifugation. For their validation, the electron microscopy, the vesicle size range and western blot for exosomes specific markers were determined. We took advantage of multiplex immunoassay as well as LC-MS/MS to analyze the protein cargo of isolated exosomes. Results We confirmed the presence of exosomes in both SWF from BCS and IORT group. The proteomes of EXO-SWF from BCS and IORT group were compared using high resolution mass spectrometry and multiplex immunoassay. We found that the that the cargo of exosomes differs significantly between analyzed groups. Moreover we confirmed the presence of proteins (OPN, MMP-1, MMP-2, MMP-3) in BCS group that prone the tumor facilitating features in tumor bed microenvironment. Conclusion This is the first report documenting the proteome of exosomes in surgical wound fluids in BCS and IORT patients. This comprehensive proteomic approach which allows for deeper and broader analysis of protein cargo of EXO-SWF enables a better understanding of their molecular and functional significance. Moreover, the presented results may be a starting point for modifying the treatment scheme by targeting specific molecules and signaling pathways. PO-1924 Exploring the association between radiomics and gene expression in bladder cancer: a pilot study Y.P. Song 1 , T. Elumalai 1 , H. Mistry 2 , K. Reeves 2 , B. Lane 2 , M. Dubec 2 , S. Jackson 3 , C. West 2 , P. Hoskin 2 , A. Choudhury 2 , A. McWilliam 2 1 The Christie Hospital NHS Trust, Clinical Oncology, Manchester, United Kingdom; 2 University of Manchester, Division of Cancer Sciences, MANCHESTER, United Kingdom; 3 The Christie Hospital NHS Trust, Physics, MANCHESTER, United Kingdom Purpose or Objective A third of patients with bladder cancer present with advanced disease, requiring aggressive treatments. A curative treatment option is trimodality bladder preserving therapy, comprising trans-urethral resection of bladder tumour (TURBT), radical radiotherapy and radiosensitiser. Previous studies have shown that the West-24 gene signature is both prognostic and predictive of survival outcomes following bladder preservation with hypoxia modification. Imaging biomarkers have the potential for non-invasive assessment of tumour biology while allowing assessment of whole tumours. To date, there have been no published studies on the association between radiomic biomarkers and gene expression in bladder cancer. Materials and Methods 10 patients treated radically with concurrent chemoradiotherapy for histologically confirmed muscle-invasive bladder cancer (MIBC) were included. Whole transcriptome sequencing using Clarion S transcriptomics was carried out on tumour samples from pre-treatment TURBT. West-24 signature score and expression of individual genes making up the gene signature were evaluated. MRI scans were carried out at 4 timepoints during treatment on 1.5T Aera Siemans scanner. 3D T2 sequences were obtained. The tumour bed and whole bladder wall were contoured by two independent observers on Raystation 7R. 93 features were extracted from the bladder wall and tumour bed using pyRadiomics. Next, unsupervised feature selection removed features with low intraclass correlation coefficient (ICC) between the two observers and between bladder wall and tumour. Unsupervised feature selection removed volume-correlated and redundant features, using Spearman’s rank correlation coefficient. Remaining features were analysed with gene expression using Pearson correlation. Due to small sample size, multiple hypothesis testing was not performed. Results 19 of 93 features demonstrated a high ICC and remained after feature reduction. Levels of expression of 8 of these 19 features differed between tumour bed and bladder wall with no overlap of interquartile range. Expression of Gray Level