The risk for secondary cancers in patients treated for prostate carcinoma - An analysis with the competition dose response model

Abstract

The risk for radiation-induced cancers has become increasingly important as patient survival following radiotherapy has increased due to the advent of new methods for early detection and advanced treatment. Attempts have been made to quantify the risk of cancer that may be associated with various treatment approaches, but the accuracy of predictions is rather low due to the influence of many confounding factors. It is the aim of this paper to investigate the impact of dose heterogeneity and inter-patient anatomical heterogeneity that may be encountered in a population of patients undergoing radiotherapy and are thought to influence risk predictions. Dose volume histograms from patients treated with radiation for the carcinoma of the prostate have been used to calculate the risk for secondary malignancies using a competition dose-response model previously developed. Biologically-relevant parameters derived from clinical and experimental data have been used for the model. The results suggested that dose heterogeneity plays an important role in predicting the risk for secondary cancer and that it should be taken into account through the use of dose volume histograms. Consequently, dose-response relationships derived for uniform relationships should be used with care to predict the risk for secondary malignancies in heterogeneously irradiated tissues. Inter-patient differences could lead to considerable uncertainties in the shape of the relationship between predicted risk and average tissue dose, as seen in epidemiological studies. They also lead to rather weak correlations between the risk for secondary malignancies and target volumes. The results stress the importance of taking into account the details of the clinical delivery of dose in radiotherapy for treatment plan evaluation or for retrospective analyses of the induction of secondary cancers. Nevertheless, the levels of risks are generally low and they could be regarded as the price of success for the advances in the radiotherapy of the prostate. © 2009 Springer-Verlag.