1 “Al. I. Cuza” University, Faculty of Physics, 700506 Iasi, Romania 2Spitalul Clinic Județean de Urgențe “Sf.Spiridon”,Iasi, Romania

Even though radiotherapy is known as the most common treatment of cancer it is often practiced in combination with chemotherapy or immunotherapy. In the frame of radiotherapy master course the students could learn about the main issues of radiotherapy efficiency, especially on radiosensitisers and radioprotectors. They have to understand that, although many cases are successfully treated, failures in local control do occur so that even a modest improvement in the relative radio sensitivity of tumors cells would result in a substantial therapeutic gain. In addition, the presently practiced fractionated dose schedule for cancer treatment – that the students have learnt from radiobiology course usually extends over a long period causing hardships and economic difficulties to patients in developing countries who often have to travel long distances for their treatment. It would therefore be desirable to shorten the period of treatment – and radiosensitizers offer some hope in these directions. To understand that successful exploitation of radiosensitizers and protectors in radiotherapy depends on selective effect of these compounds on tumors and normal tissues respectively, the students need some chemistry and molecular biology knowledge. The presentation of the subject could be accomplished using graphical curves from literature where the temporal evolution of radiation effects is discussed as a function of radiosensitisers and radioprotectors. The main molecular mechanisms of radioprotectors should be presented: competition and complexation – in the larger context regarding the influence of the irradiation conditions on the biological effects of radiations.