An analysis of synergistic sensitization.

The molecular theory of cell survival predicts that a synergistic interaction on cell survival may be expected when DNA-damaging agents are used in combination with ionizing radiation. The synergism is expected to result from the interaction of DNA single-strand damage induced by the agent and single-stand breaks induced by the radiation. Mathematically this is expressed by an increase in the alpha coefficienty of the survival equation S = exp - (alpha D + beta D2), the beta coefficient remaining constant. Two examples of synergistic interaction with ionizing radiation are analysed, a chemical used in tumour therapy and ultra-violet light. The implication of this analysis for sensitization in radiation therapy are discussed.