ESTRO 36 Abstract Book

S549 ESTRO 36 _______________________________________________________________________________________________

Results While in 2D cultures of 518A2 melanoma cells, the comparator substance cilengitide showed to be more efficient than our novel compound NIA (IC50 value of 0,65µM), it had no inhibitory effect in 3D spheroid culture up to 50µM. Comparatively NIA revealed to have similar effectiveness in 2D as well as 3D cultures, both in the low micromolar range. During monitoring of spheroid growth, NIA treated spheroids initially depicted a growth retardation, before cells started to disintegrate and die. The radiosensitivity of 518A2 melanoma cells was found to be similar in both culture conditions. Conclusion Similar differences in drug response and efficacy between 2D and 3D cell culture environments have been reported for various anti-cancer substances as well as for some radiation exposure endpoints. However, other endpoints may - in a treatment-related manner - be depending on the culture system used. We thus plan to perform further comparative studies on survival-dependent aspects (apoptosis, intracellular signaling, and others) with integrin antagonists alone as well as in combination with irradiation in 2D cell culture versus 3D spheroids. PO-0995 Estimation of radiobiology parameters of infiltrative low-grade gliomas WHO Grade II. S. Milyukov 1 , Y. Lysak 2 , G. Panshin 2 , N. Kharchenko 1 , Z. Tsallagova 2 , T. Izmailov 2 1 Peoples’ Friendship University of Russia, Department of oncology and roentgenoradiology, Moscow, Russian Federation 2 Russian Scientific Center of Roentgenoradiology of Russia, Research department of innovative technologies of radiotherapy and chemoradiation treatment of malignant tumors, Moscow, Russian Federation Purpose or Objective Determine the value of radiobiological parameters of infiltrative low-grade gliomas WHO Grade II Material and Methods In total (the data from) 5 clinical studies: EORTC 22844 (Karim AB et al., 1996.), EORTC 22845 (van den Bent MJ et al., 2005), NCCTG 86-72-51 (Shaw E et al., 2002), the RTOG 9802 (Shaw EG et. al., 2012), the study on the hyperfractionated radiotherapy (Jeremic B et. al., 1998), and selected data from our database were used for the calculation radiobiological parameters of LGG. In total, our study included 870 patients. All patients received surgery (1-phase treatment) and radiotherapy (2-phase treatment). Following radiobiological parameters of radiotherapy were used for the calculation: dose per fraction, total dose of radiotherapy, total number of treatment days, 5-year progression-free survival. Results Following radiobiological parameters of infiltrative low- grade gliomas WHO Grade II were calculated: α, β, α/β, Td, D prolif, Tk, N clonogens. Following values were calculated (95% Cl): α (Gr – 1 ) = 0,096 (0,08–0,11), β (Gr –2 ) = 0,014 (0,012-0,018), α/β (Gr) = 6,8 (4,3-9,2), T d (days) = 21,3 (18,3-26,4), D prolif (Gr) = 0,27 (0,21-0,35), T k (days) = 44 (34-55), N clonogens = 2,18·10 3 (1,2-5,3) ·10 3 . Conclusion The calculated values of radiobiological parameters give a better idea of the biological properties of the low-grade gliomas and estimate as accurately as possible of the total dose of radiotherapy using a linear-quadratic model.

Poster: RTT track: Patient preparation, positioning and immobilisation

PO-0996 Accuracy of an optical surface monitoring device to reduce daily imaging of breast cancer patients J. Sharpe 1 , A. Tini 1 , A. Moreira 1 , I. Pytko 1 , C. Winter 1 , M. Guckenberger 1 , C. Linsenmeier 1 1 University Hospital of Zurich, Radiation Oncology Clinic, Zurich, Switzerland Purpose or Objective To further test the positioning accuracy of an optical surface monitoring device called Align RT for the treatment of breast cancer patients. The data will then be analyzed to determine if the daily positioning with Align RT is accurate enough to allow for fewer weekly MV imaging of breast radiotherapy patients. Material and Methods 16 breast cancer patients were treated using 3D tangential fields. Patients were positioned supine on the breast board using an optical surface detector (Align RT). After positioning, MV imaging and bone match on the chest wall was done to verify the patients position, and corrected accordingly. All shifted values were recorded. The Align RT system consists of 6 cameras, which acquire the patients’ position in 2D, and a computer vision algorithm, which reconstructs the image into 3D. The patients’ reference surface was imported from the CT scan and the region of interest of the treated area was selected. The patient was positioned by using the Monitoring mode in Align RT and driving couch values until pre-shift Align RT deltas were as close to zero as possible. The Vertical (VRT), Lateral (LAT), Longitudinal (LNG) shift values generated from the MV images equal to or less than 5mm were marked as falling within our accepted tolerance for breast patients. This data was further analyzed to conclude if it would be acceptably accurate enough to reduce daily imaging. Results Out of the 16 patients involved in the study, a total of 213 fractions were treated using Align RT. Of these fractions, 201 (94.4%) had MV shift values, in all directions, within our 5mm tolerance. 209 of 213 fractions (98%) were within a 6mm tolerance or less. The largest shift observed was 9.5mm in the lateral direction, however the most frequent axis that fell out of tolerance were VRT and LNG. The most failed fractions (fractions with shift greater than 5mm) observed from an individual patient was 3 out of her 25 recorded fractions. 9 of the 16 patients were treated with all fractions within tolerance. Conclusion The data was found to be very consistent across all patients, with 9 from 16 patients having all MV shifts equal to or less than 5mm in all directions after using Align RT for positioning and the remaining having minimal fractions outside this tolerance. This data suggests a strong argument for reducing daily imaging with breast patients being positioned with Align RT. Reducing daily imaging to 2-3 times per week in combination with daily positioning using Align RT would then be valuable in reduction of both excess dose to the patient and treatment time on the Linear accelerator. PO-0997 Improving shoulder positioning in a 5-points mask. L. Mesch 1 , S. Hol 1 , G. D'Olieslager 2 , C. Buijs 1 , D. Washington 1 1 Dr. Bernard Verbeeten Instituut, Department of Radiation Oncology, Tilburg, The Netherlands 2 Dr. Bernard Verbeeten Instituut, Department of medical Physics & Engineering, Tilburg, The Netherlands