ESTRO 2023 - Abstract Book

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ESTRO 2023

Results Median age 69 years (46-84). Seventy-seven patients received androgen deprivation therapy, 33% as neoadjuvant. LDR: 100% low risk. HDR: 44% low risk and 56% favorable intermediate risk. Median follow-up was 70 months (5-202). Median PSA at diagnostic 7.12 ± 2.96 ng/ml. Median D90 LDR 180.5 ± 9.6 Gy. Median D90 first implant HDR 14.49± 0.3 Gy. Median D90 second implant HDR 14,50 ± 0,30 Gy. Ninety-five patients (68%) were include in group 1, 27 patients (19%) in group 2, 8 patients (6%) in group 3 and 9 (7%) in group 4. Median nPSA group 1 was 0.08 ± 0.63 ng/ml, 0.30 ± 0.06 ng/ml in group 2, 0.57 ± 0.14 ng/ml in group 3 and 1.45 ± 0.48 ng/ml in group 4. Median time to reach nadir was 30 months (3-108) in group 1, 24 months (3-48) in group 2, 21 months (9-36) in group 3 and 12 months (3-36) in group 4. BF was observed in 4 patients (4%) of group 1 (3 patients with exclusively LF and one with LF and LNF), 4 patients (15%) of group 2 (3 LF), 4 patients (50%) in group 3 (1 LF) and 7 patients (78%) in group 4 (5 FL, 7 LNF and 6 DM). Median time to FB 73 months (21-202) in group 1, 55 months (14-164) in group 2, 52 months (54-147) in group 3 and 39 months (7-79) in group 4. Conclusion The nPSA categories provide prognostic information that identify the patients at increased risk of FB, LF, LNF and DM. Reach low nadir values at a set time point post-BT predicts improved clinical outcomes. Evaluation of nPSA in BT exclusively treatments in low risk and intermediate risk PC provided a very useful tool in the follow-up of these group of patients, in order to establish early rescues strategies. 1 Korea Advanced Institute of science and technology, IT convergence, Daejeon, Korea Republic of; 2 Yuseong Sun medical center, Department of Radiation Oncology, Daejeon, Korea Republic of; 3 Korea advanced institute of science and technology , Institute Information technology convergence , Daejeon, Korea Republic of; 4 Korea advanced institute of science and technology, Department of nuclear and quantum engineering, Daejeon, Korea Republic of Purpose or Objective Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) recommends to use Liman-Kutcher-Burman (LKB) normal tissue complication probability (NTCP) metric to predict normal tissue side effect for external radiation therapy. Many LKB NTCP models were studied and developed, we still have relatively high uncertainty. Large-scale cohort studies are necessary to overcome these model uncertainties, but many clinical facilities face low accessibility to NTCP calculations yet. Materials and Methods We have therefore developed a new calculator platform for use with Digital Imaging and Communications in Medicine (DICOM): the Universal DICOM NTCP Platform (UDNP). The UDNP accepts DICOM files generated from treatment planning by clinicians so that researchers do not need to generate dose–volume histograms (DVHs) for NTCP calculations. We have implemented two equivalent unit dose (EUD) calculation metrics in the UDNP for validation and systematic-uncertainty studies: the QUANTEC and Kutcher–Burman (KB) metrics. The QUANTEC metric calculates the EUD voxel-by-voxel, while the KB metric calculates it from the DVH curve. As the DVH curve obtained with a very-small-dose grid is the same as a listing for independent voxels, the KB metric approximates the QUANTEC metric. Because many NTCP calculation tools utilize the DVH curve, we have studied the NTCP uncertainty that arises from the of the DVH dose grid. The original KB study recommended a grid of 1 or 2 Gy for the dose–volume histogram because the computing power available at that time was limited. In the present study, we have utilized the UDNP to compare the KB metrics obtained using dose grid s of 2, 1, 0.5, 0.01, and 0.005 Gy with the QUANTEC metric. Results When we calculated the EUD and the NTCP, we found that a dose grid of 0.005Gy gave results that are essentially identical to those obtained using the QUANTEC metric, while the difference between QUANTEC and KB with 2Gy dose grid was about 0.63Gy and 0.92% in average. However, when we changed the NTCP parameters to locate the patient EUD at the most sensitive section, the difference between the QUANTEC and 2Gy dose grid NTCP average changed to 14.44%. This implies that the EUD uncertainty may result in clinical mis indications. We also compared the QUANTEC constraints on the patients’ DVH curves, and we found that all patients’ plans were below the QUANTEC constraints, even though they were generated using the forward-calculation method. All the UDNP calculations were performed within one second with a common processor. We have thus successfully developed the UDNP and have used it to benchmark the KB metrics against the QUANTEC metric. Because of the systematic uncertainties we found, we recommend to use dose grid s as low as 0.005Gy. Conclusion As the UDNP is easy to use and provides the NTCP and DVH-constraint analysis functions recommended by QUANTEC, we expect the UDNP to be used for NTCP calculations and model development in cooperating clinical facilities. Poster (Digital): Normal tissue radiobiology PO-2200 Universal DICOM NTCP Platform development and its first application to NTCP accuracy study K. Choi 1 , J. Kim 2 , S. Lee 2 , H. Chang 3 , S. Cho 4

PO-2201 The functional mechanism of gut microbiota in acute radiation enteritis based on metabonomics

C. Ma 1 , X. He 1 , X. Xu 1 , J. Zhou 1