The impact of different dose–response parameters on biologically optimized IMRT in breast cancer

Abstract

The full potential of biologically optimized radiation therapy can only be maximized with the prediction of individual patient radiosensitivity prior to treatment. Unfortunately, the available biological parameters, derived from clinical trials, reflect an average radiosensitivity of the examined populations. In the present study, a breast cancer patient of stage I-II with positive lymph nodes was chosen in order to analyse the effect of the variation of individual radiosensitivity on the optimal dose distribution. Thus, deviations from the average biological parameters, describing tumour, heart and lung response, were introduced covering the range of patient radiosensitivity reported in the literature. Two treatment configurations of three and seven biologically optimized intensity-modulated beams were employed. The different dose distributions were analysed using biological and physical parameters such as the complication-free tumour control probability (P(+)), the biologically effective uniform dose (D), dose volume histograms, mean doses, standard deviations, maximum and minimum doses. In the three-beam plan, the difference in P(+) between the optimal dose distribution (when the individual patient radiosensitivity is known) and the reference dose distribution, which is optimal for the average patient biology, ranges up to 13.9% when varying the radiosensitivity of the target volume, up to 0.9% when varying the radiosensitivity of the heart and up to 1.3% when varying the radiosensitivity of the lung. Similarly, in the seven-beam plan, the differences in P(+) are up to 13.1% for the target, up to 1.6% for the heart and up to 0.9% for the left lung. When the radiosensitivity of the most important tissues in breast cancer radiation therapy was simultaneously changed, the maximum gain in outcome was as high as 7.7%. The impact of the dose-response uncertainties on the treatment outcome was clinically insignificant for the majority of the simulated patients. However, the jump from generalized to individualized radiation therapy may significantly increase the therapeutic window for patients with extreme radio sensitivity or radioresistance, provided that these are identified. Even for radiosensitive patients a simple treatment technique is sufficient to maximize the outcome, since no significant benefits were obtained with a more complex technique using seven intensity-modulated beams portals.

A graphic user interface toolkit for specification, report and comparison of dose–response relations and treatment plans using the biologically effective uniform dose

“…The inputs for the calculation of BEUD include the DVHs exported from the TPS and the dose-response parameters from the clinical database [15-22]. In the Input tab of this program, the user will first put in the comparing modalities (eq.…”

Biology Contributions Radiobiological evaluation of the influence of dwell time modulation restriction in HIPO optimized HDR prostate brachytherapy implants

“…The D 50 and γ parameters are derived from clinical materials and describe the shape of the dose-response curve, which subjects to uncertainties such as the inter-patient and intra-patient variation of radiosensitivity, setup uncertainties, accuracy of the radiobiological model, etc. [34, 35]. The uncertainties that are associated with these parameters are of 5% for D 50 , 30% for γ and 50% for s [36, 37].…”

Assessing Four-dimensional Radiotherapy Planning and Respiratory Motion-induced Dose Difference Based on Biologically Effective Uniform Dose

“…Variables α and β are the fractionation parameters of the model and account for the early and late effects expected, respectively. The dose-response parameters of the target and organs at risk used in this study were listed in Table III (20-27). …”