ABSTRACT
The rationale for conformal radiotherapy (CFRT) is straightforward to state. The goal is
to achieve a tumorcidal high-dose volume which conforms to (i.e. wraps closely around) the
planning target volume (PTV) whilst simultaneously the organs-at-risk (OARs) (which might
lie tightly adjacent to the PTV) receive a dose sufficiently low as not to cause any complications.
The concept behind this rationale is that if the difference between the relative dose received by
the PTV and the OARs can be made as large as possible, then the dose to the PTV can be
escalated with consequent expectation of a higher tumour control probability (TCP) without
causing unwanted radiation damage to normal-tissues (i.e. a low normal-tissue complication
probability (NTCP)). Today the words conformal radiotherapy have replaced the somewhat
older term conformation radiotherapy coined by Takahashi (1965) over 35 years ago.
