Chemical modifiers of cancer treatment

It is clear that the investigators involved in chemical modification have reached an historical turning point in radiobiology. Studies in the 1960s concentrated on physical and chemical radiobiology, studying dose response relationships and initial chemical reactions. More recently, the area of biochemical radiobiology has been entered and studies of cellular modification of the initial events and cellular repair mechanisms have been initiated. The future would appear to belong to biochemical modulation. The ability to increase or decrease the various cellular components through enzyme blocking or stimulation gives much greater power to our abilities to chemically modify radiation and cytotoxic agents in the future. We are thus come from the winding country lane of sensitizer development to the complex city expressway of chemical modification. Non-nitro-compounds and pyrimidine analogs have entered the field, and cellular biochemistry has assumed a major role in our future progress. Although misonidazole has overall been a clinical failure, the investment in its laboratory and clinical study has opened up a whole new field of chemical modification based on sound biochemical principles.