Applications of Recent Advances in Nuclear Physics to Cancer Research

THE immediate influence of the recent developments in nuclear physics upon the study of cancer is likely to be due to the provision of new and powerful tools for investigation and of new agents with therapeutic possibilities. It is more difficult to assess the significance of the studies of the mechanism of the biological action of radiations necessitated by the protection of large numbers of industrial workers from the radioactive hazards involved in making atomic bombs (R. S. Stone, 1946). These subjects have been discussed in two previous papers (Mitchell, 1946, a, b). The present review includes more recent published information, and emphasizes different aspects. The most important technical development is, of course, the chain-reacting "pile" (Smyth, 1945). This provides a method of preparation of very large amounts of many radioactive isotopes. It seems likely that these substances will ultimately become widely applied in medicine and biology as: 1. Tracers for the study of normal and pathological metabolic processes and in investigations in pharmacology and therapeutics. 2. Artificial radioactive sources mainly for use in radiotherapy as a substitute for radium. 3. Agents with therapeutic possibilities such as radio-phosphorus and the radio-iodines, and probably much better, suitable organic compounds containing radioactive isotopes, whose action depends on selective concentration of the radioactivity in particular cells. The separation on the industrial scale of non-radioactive isotopes and the practical development of the mass spectrometer open new possibilities of isotopic tracer research where radioactive effects are undesirable, as in many clinical investigations, or where, as in the case of nitrogen and oxygen, no suitable radioactive isotopes exist. The cyclotron still remains an essential instrument both for the production of small amounts of certain isotopes and as a source of fast neutrons for therapeutic trials in cancer and related diseases. It is by no means certain that the frequency modulated cyclotron will be useful as a therapeutic source of fast 1