Benedikt Thomann1, Ilias Sachpazidis2, Khodor Koubar2, Constantinos Zamboglou3, Panayiotis Mavroidis4, Rolf Wiehle2, Anca-Ligia Grosu3, Dimos Baltas2. 1. Division of Medical Physics, Department of Radiation Oncology, Medical Center, Faculty of Medicine, University of Freiburg, German Cancer Consortium (DKTK) Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany. Electronic address: benedikt.thomann@uniklinik-freiburg.de. 2. Division of Medical Physics, Department of Radiation Oncology, Medical Center, Faculty of Medicine, University of Freiburg, German Cancer Consortium (DKTK) Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany. 3. Department of Radiation Oncology, Medical Center, Faculty of Medicine, University of Freiburg, German Cancer Consortium (DKTK) Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany. 4. University of North Carolina at Chapel Hill, Department of Radiation Oncology, USA.
Abstract
PURPOSE: To evaluate the influence of radioresistance and intrafractional movement on the tumour control probability (TCP) in IMRT prostate treatments using simultaneous integrated boosts to PSMA-PET/CT-delineated GTVs. MATERIALS AND METHODS: 13 patients had PSMA-PET/CT prior to prostatectomy and histopathological examination. Two GTVs were available: GTV-PET and GTV-histo, which is the true cancer volume. Focused IMRT plans delivering 77 Gy in 35 fractions to the prostate and 95 Gy to PTV-PET were produced. For random portions of the true cancer volume, α and α/β were uniformly changed to represent different radiosensitivity reductions. TCP was calculated (linear quadratic model) for the true cancer volume with and without simulated intrafractional movement. RESULTS: Intrafractional movement increased the TCP by up to 10.2% in individual cases and 1.2% averaged over all cases for medium radiosensitivity levels. At lower levels of radiosensitivity, movement decreased the TCP. Radiosensitivity reductions of 10-20% led to TCP reductions of 1-24% and 10-68% for 1% and 5% affected cancer volume, respectively. There is no linear correlation but a sudden breakdown of TCPs within a small range of radiosensitivity levels. CONCLUSION: TCP drops significantly within a narrow range of radiosensitivity levels. Intrafractional movement can increase TCP when the boost volume is surrounded by a sufficiently high dose plateau.
PURPOSE: To evaluate the influence of radioresistance and intrafractional movement on the tumour control probability (TCP) in IMRT prostate treatments using simultaneous integrated boosts to PSMA-PET/CT-delineated GTVs. MATERIALS AND METHODS: 13 patients had PSMA-PET/CT prior to prostatectomy and histopathological examination. Two GTVs were available: GTV-PET and GTV-histo, which is the true cancer volume. Focused IMRT plans delivering 77 Gy in 35 fractions to the prostate and 95 Gy to PTV-PET were produced. For random portions of the true cancer volume, α and α/β were uniformly changed to represent different radiosensitivity reductions. TCP was calculated (linear quadratic model) for the true cancer volume with and without simulated intrafractional movement. RESULTS: Intrafractional movement increased the TCP by up to 10.2% in individual cases and 1.2% averaged over all cases for medium radiosensitivity levels. At lower levels of radiosensitivity, movement decreased the TCP. Radiosensitivity reductions of 10-20% led to TCP reductions of 1-24% and 10-68% for 1% and 5% affected cancer volume, respectively. There is no linear correlation but a sudden breakdown of TCPs within a small range of radiosensitivity levels. CONCLUSION:TCP drops significantly within a narrow range of radiosensitivity levels. Intrafractional movement can increase TCP when the boost volume is surrounded by a sufficiently high dose plateau.
Authors: Constantinos Zamboglou; Benedikt Thomann; Khodor Koubar; Peter Bronsert; Tobias Krauss; Hans C Rischke; Ilias Sachpazidis; Vanessa Drendel; Nasr Salman; Kathrin Reichel; Cordula A Jilg; Martin Werner; Philipp T Meyer; Michael Bock; Dimos Baltas; Anca L Grosu Journal: Radiat Oncol Date: 2018-05-02 Impact factor: 3.481
Authors: Simon K B Spohn; Ilias Sachpazidis; Rolf Wiehle; Benedikt Thomann; August Sigle; Peter Bronsert; Juri Ruf; Matthias Benndorf; Nils H Nicolay; Tanja Sprave; Anca L Grosu; Dimos Baltas; Constantinos Zamboglou Journal: Front Oncol Date: 2021-05-14 Impact factor: 6.244