Radiobiological compensation of treatment errors in radiotherapy

The linear quadratic model of radiation effect and the biologically effective dose concept can sometimes be used to provide radiobiological compensation for errors that have occurred in radiotherapy dose delivery. The associated mathematics is not complex, but there are important subtleties, which can lead to misunderstanding and erroneous corrections if the processes involved are not properly understood. Unfortunately, training in this area is, at best, patchy. In this article, several worked examples are used to demonstrate the principles involved in establishing error compensations, including cases in which dose distribution is itself changed as a result of the error. Compromise solutions are sometimes necessary, and close liaison between the clinician, physicist and (where possible) radiobiologist is necessary to obtain the best (and safest) compensation.