Dose, effect severity, and imparted energy in assessing biological effects.

Because of the widespread efforts in cancer radioepidemiological studies to attach a value of absorbed dose to each exposed individual, the notion seems to have become prevalent that dose plays an essential role in the medical determination of the diagnosis and prognosis of the individual. This view is enhanced by the fact that, while the present quantities and units for radiological physics were developed in the context of the acute effects of large exposures to radiation, e.g., in radiotherapy where they still apply well, these same quantities and units have been used, without modification, to apply to cancer radioepidemiology in the context of low level irradiation. A principle purpose of the present communication is to show that, in medicine, dose plays a limited role even in the deterministic application of therapeutic agents, and that diagnosis and estimates of prognosis in medicine are based, not on dose, but on the severity of effect on, or damage to the organ or organs involved in a particular medical condition. Thus it is "going backward" to view estimates of the severity of effect, e.g., the fraction of cells with abnormalities, or killed, as a "biological dosimeter," rather than as a quantitative estimate of the severity of effect. The use of biological indicators is of maximum value in noncancerous disease or injury in which the severity of an effect causative for organ failure and a consequent quantal, e.g., a lethal response in the individual, can be measured with increasing accuracy by modern medical techniques.(ABSTRACT TRUNCATED AT 250 WORDS)