IMRT, hypofractionated radiotherapy and stereotactic radiotherapy: Technique, indications, and results

Abstract

The major technological advance in external beam radiotherapy in the 1990s was the introduction of conformal radiotherapy. For the first time, the high-dose volume was not constrained to be cuboid in shape, because the radiotherapy beam collimators were multi-leaf (instead of single leaf), the radiotherapy beam could be irregular in shape and did not have to be rectangular or square. The high dose volume could thus ‘conform’ more closely to the shape of the tumour, by tailoring the shape of the beam using multileaf collimators (MLCs); when introduced, this held the promise of reducing the total volume of tissue irradiated, and the randomised trial carried out by the Royal Marsden Hospital confirmed that this was, indeed the case [14]. However, as well as reducing treatment toxicity, conformal radiotherapy also permitted the alternative strategy of dose escalation, which was successfully deployed in a number of randomised trials and is now regarded as standard practice. The current European Association of Urology guidelines recommend a dose of 76-78 Gy in combination with ADT for intermediate-risk and high-risk disease, when given in ‘standard’ fraction sizes of 1.8-2 Gy per fraction [42].