Proposed UK trial needs to define techniques as well as numbers of treatments 

In the early 1920s Regaud discovered the benefits of radiation treatment fractionation—that is, splitting the dose into several treatments over several days—when he was trying to sterilise the testes of rams with radiation without necrosing the scrotal skin.1 During the 1930s radiotherapy changed from a dangerous mystery that put patients and staff at risk2 to a therapeutic modality with a scientific basis. This was an era when radiotherapy fractionation and treatment guidelines were empirically developed from clinical observation tempered by pragmatic issues such as machine availability. Since then the science of radiotherapy has advanced considerably, but suspicions that pragmatic considerations still weigh too heavily are surrounding a proposed British trial of radiotherapy fractionation in breast cancer.

Early randomised clinical trials in cancer—and, therefore, in radiotherapy—reflected the management arguments of the time and addressed questions about what patients to treat with which modality. Trials of radiotherapy process—techniques, fractionation, overall treatment time—had to wait until the 1970s, when radiobiology was suggesting that these factors were crucial. In 1978 Withers showed for pig skin that acute radiotherapy reactions were worse after large numbers of small dose fractions than after a few high dose fractions, while the late reactions were worse after the latter.3 Therefore, side effects depended on total dose and fraction size. Other evidence suggested that tumour cells could repopulate a tumour rapidly during radiotherapy. Hence, prolonging treatment could be …