Advances in radiotherapy

#### Summary points Radiotherapy plays an important role in the care of patients with cancer and forms part of the management of 40% of patients cured of their disease.1 Advances have been made in the past two decades, as improvements in engineering and computing have enabled technologies such as intensity modulated radiotherapy (IMRT), image guided radiotherapy (IGRT), and stereotactic radiotherapy (SRT) to be used in routine clinical practice. This article explains newer radiotherapy techniques and aims to enable general practitioners and non-specialist clinicians to advise patients who come to them with questions. It will focus on external beam radiotherapy (EBRT), which is the most common form of treatment, delivered to 125 000 patients a year in England.2 #### Sources and selection criteria This article is an evidence based review of clinical radiotherapy. We searched PubMed and the Cochrane databases between 1990 and 2012 using the search terms radiotherapy, intensity modulated radiotherapy, image guided radiotherapy, stereotactic radiotherapy, and proton beam therapy to identify observational studies, randomised trials, meta-analyses, and systematic reviews. X rays are a form of electromagnetic radiation that deliver their energy through waves called photons. These photons are produced by accelerating a stream of electrons and colliding them with a metal target. High energy photons produce secondary electrons in human tissue. Electrons cause DNA damage which, if not repaired, proves fatal at cell division. Absorbed …