The NSD concept and radioresistant tumours

According to the NSD Concept (Ellis, 1966, 1971) it is possible to determine the dose per fraction for a given number of fractions in a given time for a certain biological effect on the normal connective tissue. In many human neoplasms, apart from certain radiosensitive ones such as Hodgkin's disease, it is only possible to achieve tumour tolerance (i.e., local cure) by reaching or exceeding normal tissue (i.e., connective tissue) tolerance. Certain neoplasms are acknowledged to be “radioresistant” to the conventional schedules of radiotherapy. Using the NSD formula it is possible to decide on other schedules the effects of which lie within normal tissue tolerance.