Three-Dimensional Conformal Radiotherapy in Treatment of High Grade Glioma

Abstract

3-D conformal radiotherapy (3-D CRT) is the term used to describe the design and delivery of radiotherapy treatment plans based on 3-D image data with treatment fields individually shaped to treat only the target tissue. The European Dynarad consortium has proposed that the complexity of radiotherapy planning and treatment methodologies can be captured in four levels. Level 0 represents basic radiotherapy where no attempt is made to shape the treatment fields and as such cannot be described as conformal. This level will not be considered further in the current publication. Conformal radiotherapy permits the delivery of a radical dose of radiotherapy while limiting the dose to normal tissue structures, thus minimising the adverse effects of treatment. Its principle benefit therefore is to patients who are to be given potentially curative radiotherapy. Where radiotherapy is being given with palliative intent the prescribed total doses are usually lower and the adverse effects of palliative radiotherapy are therefore likely to be less. For this reason conformal radiotherapy is not often used when delivering palliative treatment, although it is always desirable to minimise the volume of non target tissue that is irradiated. Conformal radiotherapy can be regarded as a step towards intensity modulated radiotherapy (IMRT). However, the delivery of IMRT, where fields are made up of multiple beamlets, is considerably more costly than conformal radiotherapy and requires an even higher level of expertise. There is considerable evidence for the benefits of 3-D CRT, but the benefits of IMRT are less well established. The incremental benefits in the transition from conventional radiotherapy to 3-D CRT are therefore substantially greater than those achieved in the transition from 3-D CRT to IMRT. It is therefore recommended that the implementation of 3-D CRT should be given priority over the implementation of IMRT