ESTRO 37 Abstract book

ESTRO 37

S595

PO-1060 Leukocytosis correlates negatively with T-cell infiltration and prognosis in anal cancer D. Martin 1 , F. Rödel 1 , R. Winkelmann 2 , P. Balermpas 1 , C. Rödel 1 , E. Fokas 1 1 Klinikum der Johann Wolfgang Goethe Univ, Department of Radiotherapy and Oncology, Frankfurt, Germany 2 Klinikum der Johann Wolfgang Goethe Univ, Senckenberg Institute for Pathology, Frankfurt, Germany Purpose or Objective Peripheral blood leukocytosis has been implicated in promoting tumor progression leading to worse survival in several malignancies including anal squamous cell carcinoma (ASCC) but the mechanisms behind this phenomenon remain largely unexplored.The role of the immune tumor microenvironment (TME) in mediating cancer development and progression gained attraction in recent years. The positive prognostic impact of tumor infiltrating lymphocytes (TIL) has been reported in in ASCC and other malignancies, as well. In contrast, myeloid cells like neutrophils remain unexplored in ASCC. Neutrophils aid tumor progression and resistance to conventional anticancer treatments by mediating angiogenesis and suppression of CD8+ TIL mediated antitumor immunity via secretion of inhibitory factors. Material and Methods We examined the prognostic role of pretreatment white blood cell (WBC) count and clinicopathologic parameters in the context of CD8+ tumor-infiltrating-lymphocytes (TIL) and MPO+ tumor-associated neutrophils (TAN) in 79 patients with anal squamous cell carcinoma (ASCC) treated with definitive chemoradiotherapy (CRT) at our department. TIL and TAN were analyzed in pretreatment FFPE tissue. Results After a median follow-up of 26 months, leukocytosis correlated with advanced T-stage (p < 0.001) and N-stage (p < 0.001), and predicted for worse distant-metastasis- free survival (p = 0.006), disease-free-survival (DFS, p = 0.029) and overall survival (p = 0.013). Importantly, leukocytosis was associated with a lower intraepithelial CD8+ TIL density (p = 0.014), whereas low CD8+ TIL expression in the intraepithelial compartment was associated with worse DFS (p = 0.028). Additionally, high TAN expression in the peritumoral compartment was associated with a significantly lower density of CD8+ TIL (p = 0.039), albeit TAN expression lacked prognostic value. Conclusion White blood cell count constitutes an important prognostic marker in ASCC patients treated with chemoradiotherapy. In conjunction with intratumoral TIL and TAN, these data provide for the first time important insight on the correlation of peripheral blood leukocytosis with the intratumoral immune contexture, and could be relevant for future patient stratification using immunotherapies. PO-1061 Evofosfamide sensitizes esophageal carcinomas to radiation without increasing normal tissue toxicity L. Spiegelberg 1 , R. Biemans 1 , N. Lieuwes 1 , R. Niemans 1 , J. Theys 1 , A. Yaromina 1 , F. Verhaegen 1 , P. Lambin 1 , L. Dubois 1 1 Dept. of Radiotherapy, GROW – School for Oncology and Developmental Biology- Maastricht Comprehensive Cancer Centre- Maastricht University Medical Centre, Maastricht, The Netherlands

repair mechanism, and downregulation of angiogenesis of concurrent BZE235 and RT.

PO-1059 octaarginine modified gold nanoparticles enhance the radiosensitivity of colorectal cancer cell X. Zhang 1 , R. Yang 1 , H. Wang 1 1 Peking University Third Hospital, Department of Radiation Oncology, Beijing, China Purpose or Objective To investigate the effectiveness and mechanisms of octaarginine (R8) modified gold nanoparticles (GNPs) radiosensitization on colorectal cancer cell line LS180 to megavoltage radiotherapy in vitro. Material and Methods The synthesized GNPs were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), ultraviolet-visible spectrometer (UV-Vis). Inductively coupled plasma mass spectroscopy (ICP-MS) was used to measure the quantities of GNPs uptake by LS180 cells. Cell counting kit-8 was used to assess the cytotoxicity of GNPs. Clonogenic assay was used to confirm the radiation enhancement effect of GNPs on LS180 cells. The cell cycle distribution, apoptosis, reactive oxygen species (ROS) level and mitochondrial membrane potential were analyzed by flow cytometry to further explore the mechanisms of radiosensitization of GNPs. Results TEM showed that the diameter of PEG-GNPs-R8 was 6.3±1.1nm (mean ± SD). Hydrodynamic diameter of PEG- GNPs and PEG-GNPs-R8 were 19.7±2.8nm and 27.8±1.8nm. The surface plasmon resonance peaks of PEG-GNPs, PEG-GNPs-R8 were 515nm and 525nm, respectively. ICP-MS indicated that LS180 cells uptake more PEG-GNPs-R8 than PEG-GNPs in one hour (2.29±0.17 VS 0.32±0.06, ×10 5 /cell). GNPs have little cytotoxicity with a concentration below 800 nM. In clonogenic formation assay, PEG-GNPs-R8 combined with radiation induced a significant growth inhibition compared with radiation only group and the sensitizer enhancement ratios were 1.59 and 1.21, respectively. Flow cytometry showed that PEG-GNPs-R8 could help radiation arrest more cells in the G2/M phase (32.3±1.8 VS 41.9±3.3, P<0.05) and induced more cells apoptosis (10.0±1.4 VS 57.5±1.7, P<0.001). The ROS level was higher in the PEG- GNPs-R8 and radiation treated group than that in the radiation only group (5185.7±305.1 VS 21087.3±1288.9, P<0.001). The PEG-GNPs-R8 and radiation treated group showed lower mitochondrial membrane potential than the radiation only group (28.2±2.5 VS 67.9±7.2, P<0.001). Conclusion Octaarginine-modified gold nanoparticles could be internalized by LS180 cells in one hour with little cytotoxicity and the number of PEG-GNPs-R8 per cell is about seventh times as much as that of PEG-GNPs, leading to significant radiosensitization effects in combination with megavoltage radiation in vitro. PEG- GNPs-R8 may enhance the radiosensitization by causing cell cycle disruption and inducing apoptosis. Increased ROS level caused by PEG-GNPs-R8 and radiation exposure may be the initiator.

Poster: Radiobiology track: Radiobiology of cancer (others)