Intensity-modulated radiation therapy: the inverse, the converse, and the perverse

Intensity-modulated radiation therapy (IMRT) is a refinement of current radiotherapy techniques rather than a major breakthrough. The term IMRT includes several different techniques that all share with classical arc therapy the principle of using multiple fields to reduce the dose to normal tissues, but integrating to a higher dose throughout the tumor volume itself. This paper reviews not only the putative upside but also the downside of the development of IMRT. Theoretical, practical, and cost considerations, both positive and negative, are discussed. There are several issues to be considered, but the most important perversely predict a significant increase in radiation-induced neoplasms, resulting not only from larger volumes of tissue exposed to more modest but still mutagenic doses, but also from a significant increase in total body dose from leakage, because the beam is typically on for a considerably longer period of time than is conventional. A plea is made for radiation oncologists to maintain a strong biologic and cellular orientation as oncology rapidly becomes more molecular in its orientation.