Experimental radiobiology of ion beams

 


In treatment planning, the increased effectiveness of ion beams is considered by the relative biological effectiveness (RBE). As the RBE depends on ion species, linear energy transfer (LET), dose as well as on various biological factors, it is calculated by biomathematical models. These models were initially developed based on in vitro data but need to be further validated in vivo. Our group performs systematic dose response studies at the Heidelberg Ion Beam Therapy Center (HIT) to determine preclinical RBE-values in normal tissues and tumors as a function of the most important physical and biological parameters. For preclinical normal tissue, the RBE is determined at different positions within a 6 cm spread-out Bragg peak (SOBP) using different dose levels and ion species. The results are used to benchmark predictions of clinically applied RBE-models. For preclinical tumors, the impact of hypoxia, tumor differentiation and tumor growth on local tumor control is determined. These experiments are supported by imaging studies to identify predictive parameters for normal tissue and tumor response. Further investigations on the histological and molecular level are performed to identify the mechanisms.
         
    Figure 1. RBE of late normal tissue reactions: benchmarling of the LET and dose-dependence. ©Saager 2020

 

 
Figure 2. Dependence of proton RBE on LET ©Saager 2018

 

 

 

Figure 3. Dose dependence of the RBE for three sublines of the same tumor

in comparison with the RBE of normal tissue published in Saager 2020

Selected publications

  • Glowa C., Peschke P., Brons S., Debus J., Karger C.P.: Effectiveness of fractionated carbon ion treatments in three rat prostate tumors differing in growth rate, differentiation and hypoxia. Radiotherapy and Oncology 2021 (in press)
     
  • Saager M., Peschke P., Brons S., Debus J., Karger C.P.: Determination of the proton RBE in the rat spinal cord: Is there an increase towards the end of the spread-out Bragg peak? Radiotherapy and Oncology 128, 115–120, 2018 https://www.sciencedirect.com/science/article/pii/S0167814018301348?via%3Dihub

 

Reviews

  • Karger C.P., Glowa C., Peschke P. Kraft-Weyrather W.: The RBE in ion beam radiotherapy: From experimental studies to clinical application. Zeitschrift für Medizinische Physik (in press)
  • Verhaegen F., Dubois L., Gianolini S., Hill M.A., Karger C.P., Lauber K., Prise K.M., Sarrut D., Thorwarth D., Vanhove C., Vojnovic B., Weersink R., Wilkens J.J., Georg D.: ESTRO ACROP: Technology for precision small animal radiotherapy research: Optimal use and challenges. Radiotherapy and Oncology 126, 471–478, 2018 https://www.sciencedirect.com/science/article/pii/S0167814017327330?via%3Dihub

 

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