ESTRO 2022 - Abstract Book

S1625

Abstract book

ESTRO 2022

Blood samples were collected before and after radiotherapy, PBM cells were investigated by flow cytometry, chromosome aberration technique was applied, protein profile of plasma samples of LDR patients were analysed by LEGENDplex assays Results Chromosome aberrations increased after radiotherapy (HDR: 3.4±0,5 to 5.5±0.8; LDR: 2.9±0.4 to 6.4±0.5; EBRT: 4.2±0.4 to 17.2±1.9; Cyberknife: 4.5±0,5 to 11.3±1.5 total aberrations/100 cells). 1.8% Gr 3 acute genitourinal (GU) side effects were observed. ≤ Gr 2 late GU toxicities were found after LDR therapy (49.0%), the less after HDR treatment (18.5%). There were 3.4% late GI side effects. IPSS questionnaire indicated the highest distress after the last fraction of teletherapies (EBRT: 16.8±1.4, Cyberknife: 16.9±1.2). Chromosome fragments frequency predicted cumulative GU toxicities 3 months after HDR therapy (Pearson corr. coeff. 0.49). Radiation induced lymphocyte apoptosis (RILA) was also measured to identify radiosensitive patients. Correlation and regression analysis showed that RILA values and chromosome aberration results are consistent. An increased level of total circulating NK cells was detected 3 months after in LDR BT patients and remains elevated up to 36 months compared to control group (CG) and pre-treatment values as well. In HDR patients mature NK cell level decreased, while degranulating and anergic NK cell levels significantly increased compared to CG. The level of lymphoid DCs showed the same pattern in both patients groups; it was increased in patients before therapy and remained unchanged up to 6 months after therapy initiation. Changes of myeloid DCs was different; in LDR patients elevated up to 12 months after the implantation, however in HDR group their level was near to average of healthy controls. Cancer significantly reduced naïve and activated CD8 cells and increased senescent CD8 and CD4 cells in HDR patients compared to CG. Effector memory T cells increased in HDR-treated patients 3 month after treatment compared to pre-treatment values, T stem cell memory, central memory and terminal memory T cell levels remained below control values up to 36 months. Conclusion Radiotherapy can influence the changes of cellular and soluble markers in LDR and HDR patient groups as well. The increases of lymphoid DCs, of the immature and degranulating NK cells are acute effects of BT, while the increase of total circulating and anergic NK cells, the activated and early-senescence CD8 and CD4 T cells and the decrease of central and terminal memory T cells are late persistent chronic effects of radiotherapy. Immunological values changed in parallel with cytogenetic parameters, suggesting their use as predictive indicator of toxicity. 1 National Cancer Centre Singapore, Division of Radiation Oncology, Singapore, Singapore; 2 SingHealth Duke-NUS, Institute for Patient Safety and Quality, Singapore, Singapore; 3 National Cancer Centre Singapore, Department of Oncologic Imaging, Singapore, Singapore; 4 National Cancer Centre Singapore, Division of Radiation Oncology, Singapore, Singapore Purpose or Objective Locally, patients undergoing prostate radiotherapy are monitored for prostate displacement using an autoscan 4D transperineal ultrasound (TPUS) probe during treatment. However, the existing TPUS probe and autoscan probe kit (ASPK) are not MRI-compatible. Hence, uncertainties due to variations in patient position and delineation of the prostate gland based on CT/MRI fusion may be introduced during treatment planning. This project aims to develop a MRI-compatible pseudo TPUS probe and ASPK to reproduce patient position during MRI to facilitate image fusion and prostate gland contouring during treatment planning. Materials and Methods The fabricated MRI-safe TPUS probe and ASPK were designed and produced in components with certain parts required to provide mechanical functions for angulation and height adjustments with similar accuracy of the existing probe used during treatment. Major components were modelled separately for producing parts using MRI-safe materials and assembly. The first prototype was printed as a singular part in both FDM and PolyJet. Selected materials must not introduce any magnetic field interference or contra-indicate MRI procedures (i.e. must not get heated up by magnetic waves). Selected manufacturing process had to consider production of parts that can ensure the rigidity and accuracy of the structure to withstand pressure on the probe at the transperineal region (i.e. Computerized Numerical Control (CNC) machined vs 3D printing). CNC process was eventually selected as 3D-printed parts tend to create material warpage that reduces the accuracy of the design and the material strength required. Results Materials that passed both image test and metal detector test: PVC, PP, ABS, Wood Meranti, Polycarbonate, with Aluminium Composite failing both image and metal detector test. Acrylonitrile Butadiene Styrene (ABS) was selected as the MRI-safe material for development of the prototype due to its durability, rigidity, strength, corrosion and impact-resistant. A test scan was performed on the MRI scanner and found to be safe and artefact-free for target used cases. (Figure 1). Two rounds of prototyping were conducted to arrive at the final product (Figure 2). Poster (digital): Patient preparation, positioning and immobilisation PO-1829 Development of a pseudo TPUS probe to improve consistency of patient positioning during MRI. E.P.P. Pang 1 , Y.K. Lim 2 , K.S.K. Heng 2 , C.H. Tan 3 , Y.A. Lin 3 , J.W.S. Chan 1 , G.K. Low 1 , J.K.L. Tuan 4