Radiobiological compensation for unintended treatment interruptions during palliative radiotherapy.

Unlike radical treatment protocols, in which radiobiological methods have been used in an attempt to overcome the risk of reduced tumour control, the problem of compensation for unintended treatment interruptions during palliative radiotherapy has received little attention. For palliative radiotherapy, unnecessarily extended treatment times could theoretically reduce the duration of tumour regression and symptomatic relief. It can be shown, using a simple argument, that the overall extension of the treatment time is likely to be at least equal to the reduced duration of benefit. In most practical instances, this duration would amount to relatively few days, but it can sometimes be as long as 1-2 weeks. The mechanisms for gap compensations are the same as for radical radiotherapy, although there is greater scope for hypo-fractionated compensation provided that tissue tolerances are respected. It is debatable whether compensation should be applied in all patients, but there might be clinical situations where this would be indicated. Such decisions might influence waiting times for other patients requiring radical radiotherapy, and therefore must be balanced against the available resources.