Ponente
Descripción
Most cancer patients worldwide who undergo radiotherapy are treated with megavoltage X-rays, though other forms of radiation (such as protons or heavy ions) are being incorporated to clinics. In all these treatment types, the absorbed dose is the fundamental magnitude to determine the effects of ionising radiation on both normal or tumor living tissues. However, a single relationship between absorbed dose and biological effects is not available because the latter depend also on factors such as the treatment fractionation, the absorbed dose rate, the radiation quality, the tumor characteristics, the environment in which it evolves, and the endpoint considered (cell survival, chromosomal aberrations, molecular damage to DNA, etc.) In general, weighting factors, such as the relative biological effectiveness (RBE), are used together with the absorbed doses to define dosimetric quantities directly related to the biological effects [1].
High-energy beams produce neutrons that may increase the dose absorbed to tissues outside the target volume and compromise critical organs with acute toxicity and late complications in treated patients. Due to the high RBE of neutrons, small neutron doses can be relevant for cancer induction. However, the uncertainties are currently too large. Besides neutron RBE is energy dependent [2] and there is a need to improve our understanding of this relationship, which also affects the radiation protection standards [3,4] and is strongly related to the data adopted for the assessment [5].
The IFMIF-DONES project is an excellent opportunity to expand our knowledge about neutron RBE. It also could provide the possibility to study cell response to both neutrons and deuterons at the energies that will be available.
In conclusion, the study of the response of cell cultures to irradiation provides valuable information that can be transferred to clinical practice. The neutron and deuteron beams that would be available at the IFMIF-DONES facility will open the possibility of analyzing situations in this respect that have never been investigated before. Cell culture irradiation and measurement of different endpoints could be carried out. The study with the new beams provided by IFMIF-DONES would complete the radiobiological information obtained by using the electron clinical accelerators of the nearby hospitals, as well as the X-ray irradiation facilities available at CAN or CIC-UGR.
[1] IAEA, TRS-461. Relative biological effectiveness in ion beam therapy. International Atomic Energy Agency. Vienna : 2008.
[2] G Baiocco, S Barbieri, G Babini, et al. The origin of neutron biological effectiveness as a function of energy. Sci Rep 2016;6:34033.
[3] ICRP. 1990 Recommendations of the International Commission on Radiological Protection. ICRP Publication 60. Ann ICRP 1991;21 (1-3).
[4] ICRP. Relative Biological Effectiveness (RBE), Quality Factor (Q), and Radiation Weighting Factor (wR). ICRP Publication 92. Ann ICRP 2003;33 (4).
[5] NRC Regulations Title 10, Code of Federal Regulations: 10 CFR. 20.1004 (2014).
