. Cellular basis and aetiology of late somatic effects of ionization radiation. Radiation -- Physiological effect. 162 R. H. MOLE pattern of cancer induction in Japanese exposed at Hiroshima wliere the induced cancer rate appears to increase with the sixth power of the age just as the natural cancer rate does (Harada and Ishida, 1960; Fig. 2). The basic hypothesis is that cancer follows the occurrence of two inde- pendent cellular events which each have a constant probability of occurrence with time if environmental conditions are constant. The first event is followed by clonal growth of cells
. Cellular basis and aetiology of late somatic effects of ionization radiation. Radiation -- Physiological effect. 162 R. H. MOLE pattern of cancer induction in Japanese exposed at Hiroshima wliere the induced cancer rate appears to increase with the sixth power of the age just as the natural cancer rate does (Harada and Ishida, 1960; Fig. 2). The basic hypothesis is that cancer follows the occurrence of two inde- pendent cellular events which each have a constant probability of occurrence with time if environmental conditions are constant. The first event is followed by clonal growth of cells all carrying this first change, the second event occurs in any of the cells carrying the first change and is inevitably followed by the development of overt cancer. The kinds of event are not further specified. 10,000 IT 5,000 2,000 o o o o o 0) 1,000 500. 200 Non-exposed (beyond 10,000m) L 20 30 40 50 60 70 Age (years) Fig. 2. Age-specific incidence rate of all malignant neoplasms in Japanese at Hiroshima (from Harada and Ishida, 1960). The upper continuous hne gives the incidence rate of all malignant neoplasms, the lower broken line the incidence rate excluding leukaemia, in those exposed between 500-1,400 metres from the hypo-centre. The interrupted line gives the inci- dence rate of all malignant neoplasms in the non-exposed (beyond 10,000 metres). If the first kind of event is produced by radiation (as well as occurring spontaneously) then irradiated individuals will carry a larger number of different clones than unirradiated people of the same age and will show the cancer incidence to be expected of older unirradiated individuals with the same number of clones. The age-specific cancer rate of the particular group of irradiated Japanese recorded by Harada and Ishida (1960) is in fact equivalent at all ages to that of unirradiated Japanese 7 to 8 years older (Fig. 2). Since. Please note that these images are extracted from scanned page images that may have been digitally
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