Abstract: Quantitative radiobiological models can be used to
assess the optimum clinical outcome from sophisticated therapeutic
modalities by calculating tumor control probability (TCP) and normal
tissue complication probability (NTCP). In this study two 3D-CRT
and an IMRT treatment plans were developed with an initial
prescription dose of 60 Gy in 2 Gy/fraction to prostate. Sensitivity of
TCP and Complication free tumor control probability (P+) to the
different values of α/β ratio was investigated for various prescription
doses planned to be delivered in either a fixed number of fractions (I)
or in a fixed dose per fraction (II) in each of the three different
treatment plans. High dose/fraction and high α/β value result in
comparatively smaller P+ and IMRT plans resulted in the highest P+,
mainly due to the decrease in NTCP. If α/β is lower than expected,
better tumor control can be achieved by increasing dose/fraction but
decreasing the number of fractions.