Comparison of conformal radiation therapy techniques within the dynamic radiotherapy project `Dynarad'

Abstract

The objective of the dynamic radiotherapy project 'Dynarad' within the European Community has been to compare and grade treatment techniques that are currently applied or being developed at the participating institutions. Cervical cancer was selected as the tumour site on the grounds that the involved organs at risk, mainly the rectum and the bladder, are very close to the tumour and partly located inside the internal target volume. In this work, a solid phantom simulating the pelvic anatomy was used by institutions in Belgium, France, Greece, Holland, Italy, Sweden and the United Kingdom. The results were evaluated using both biological and physical criteria. The main purpose of this parallel evaluation is to test the value of biological and physical evaluations in comparing treatment techniques. It is demonstrated that the biological objective functions allow a much higher conformality and a more clinically relevant scoring of the outcome. Often external beam treatment techniques have to be combined with intracavitary therapy to give clinically acceptable results. However, recent developments can reduce or even eliminate this need by delivering more conformal dose distributions using intensity modulated external dose delivery. In these cases the reliability of the patient set-up procedure becomes critical for the effectiveness of the treatment.

Use of Radiobiological Modeling in Treatment Plan Evaluation and Optimization of Prostate Cancer Radiotherapy

“…This implication indicates a parallel organization fashion for the tumours. Taking this assumption into account the overall probability of tumour control (P B ), is given by the expression (Lind et al 1999, Mavroidis et al 2000 …”

“…As a measure of the quality of a treatment plan, the mean doses and their standard deviations to the target volumes and organs at risk are usually reported, together with the minimum and maximum doses as well as some DVH-based constraints. In addition to those parameters, the present radiobiological treatment plan evaluation uses the D concept, w h i c h i s d e f i n e d a s t h e d o s e t h a t c a u s e s the same tumour control or normal tissue complication probability as the actual dose distribution given to the patient and it is derived numerically from the following expression (Mavroidis et al 2000(Mavroidis et al , 2001:…”

“…It has been demonstrated that although competing treatment plans might have similar mean, maximum or minimum doses they may have significantly different clinical outcomes (Mavroidis et al 2001). For performing a more complete treatment plan evaluation and comparison the complication-free tumor control probability (P+) and the biologically effective uniform dose ( D ) have been proposed (Källman et al 1992a, Mavroidis et al 2000. The D concept denotes that any two dose distributions within a target or OAR are equivalent if they produce the same probability for tumor control or normal tissue complication, respectively (Mavroidis et al 2001).…”

In response to ‘Behind EUD’

“…All the above mentioned problems were overcome with the introduction of the biologically effective uniform dose (/D) by Mavroidis and colleagues [7,8], which is a combination of the basic characteristics of the D eff and EUD concepts.D is the uniform dose that causes exactly the same tumor control or normal tissue complication probability as the real dose distribution on a complex target or normal tissue patient. In complex patient cases multiple targets or multiple organs at risk of different radiosensitivities are involved.…”

Variation in radiation sensitivity and repair kinetics in different parts of the spinal cord

“…For this reason, it is important to understand and identify the volume effect, which is determined by the pattern of functional organization in parallel and serial subunits. Due to its high flexibility [15] the relative seriality model is used in this work, to handle the concept of the volume effect [5,22,23]:…”