The individualization in radiotherapy: Where are we now, and where are we going?

Abstract

The synonym of the best treatment method is individualization of the treatment. Based on a description of the characteristics of the patient, his or her disease, treatment volume, etc., the best method of irradiation is proposed. The individualization could be considered in terms of the individual dose distribution and individual fractionation. However, the dose distribution and the fractionation are usually treated separately. Currently the individualization of dose distribution, thanks to development of technology, is very advanced. Several methods of Intensity Modulation Radiotherapy allowed to conform the dose distribution to the actual anatomy. Dose-painting becomes a common method of treatment. Nevertheless, due to inherent characteristic of radiation used in radiotherapy, the ideal dose distribution can’t be obtained. Proton therapy does offer improved dose conformity, compared to IMRT. Another limitation in individualisation of the dose distribution is the lack of precise (description) delineation of the tumour. Several new imaging methods (positron-emission tomography and magnetic resonance) are very promising. According to Bentzen, we are able not only to conform the dose distribution to the individual anatomy but also to deliver some additional dose to tumour subvolumes with a potential resistance. To describe this type of treatment he coined a term of dose-painting by numbers. Another area for individualization is a time pattern of the dose delivery. Several randomized trials proved the importance of overall treatment time shortening to avoid rapid tumour cell proliferation. Patient-specific fractionation schedule optimization can improve the therapeutic index at least for some patients. The new imaging and molecular data and more reliable models of tumour dynamics may help in making radiotherapy more personalized.