This thesis is focused on the predictive models of irradiation induced toxicities in intensity modulated radiotherapy. Six different NTCP models were implemented and their parameters were identified at predicting late rectal and bladder toxicities in prostate cancer. Their predictive skills have been demonstrated on both organs. Second, LKB model was used to predict the irradiation induced acute esophagitis after nun-small-cell lung cancer. Then, the benefit of using EUD in prostate cancer IMRT inverse planning was evaluated. The evaluation of the proposed approach proved that the use of EUD significantly decreased both the dose in the bladder and rectum walls. Then, the incorporation of different biological models in IMRT optimization process has been realized. Objective functions were established for different biological factors like NTCP, EUD and TCP. Obtained results show the superiority of the optimization based on biological factors over the optimization relying only on physical factors. Finally, classical NTCP models were corrected to deal with another radiobiological parameter, the α/β ratio. With this additional factor, NTCP models can be extended to predict toxicity for patients with different dose fractionation, these kinds of treatments being more and more clinically used.
