An analysis of radiation-induced malignancy based on somatic mutation.

If, as has been proposed, the factor which controls the malignant nature of a cell behaves as a recessive genetic character, a somatic mutation in the normal dominant homologous gene of a diploid cell, which carries the malignant factor, may allow the expression of the recessive malignant character. Using this proposal together with the molecular theory of cell survival, a mathematical equation is derived to provide a general description of the dose response for radiation-induced malignancy which is non-linear and peaked. The equation is based on the assumption that a radiation-induced DNA double-strand break can cause a somatic mutation or a chromosome aberration which may leave the cell in a precancerous state. The equation is used to analyse data on the radiation-induced transformation of diploid cells and extended logically to analyse data on the transformation of tetraploid cells.