When evaluating the risks of radiotherapy, we should always take into account that the patient is subjected to a potential benefit from radiotherapy. Any patient, who enters into the process of receiving radiation treatment, will be exposed to many potential sources of harm throughout the medical procedures. While the probability of harm occurring is low, the consequences of that harm can be serious for the individual patient. The combination of these two elements, probability of harm occurring and consequence when harm occurs, creates the risk the patient is subjected to.?

Major cases of accidental exposure in radiotherapy have only been reported a few times over all the years of radiotherapy activity throughout the world. These events have mostly been very well investigated and it is important that the lessons to learn from these cases are not lost as time passes.

The following sections briefly describe nine major cases of accidental exposures in radiotherapy, together with lessons learned, and resources for developing a deeper understanding of these events: