The term "cancer" designates a group of diseases having similar characteristics with one outstanding common denominator, unchecked proliferation of cells. These cells, often made up predominantly of immature or undifferentiated types, usually survive at the expense of the host. Biochemically, too, cancerous tissues may have some traits in common, such as lower pH, lower catalase levels, and an altered calcium potassium ratio; however, no general morphological or biochemical description will fit every type of cancer.

Diversities are extensive. Etiology is often unknown, latent period varies, cells grow at different rates, and, generally, these diseases show extreme differences in dependence on, or sensitivity to, hormones or chemotherapeutic agents. It is unlikely, therefore, that a single theory will be found which will adequately explain all types of cancer and hence lead to their rational control by a single agent.

The published reviews on the cancer problem, dealing with a unifying concept or with an integrated concept of carcinogenesis, help the investigator by giving a descriptive picture of the cancer phenomena. Those reviews on possible mechanisms of action of anti cancer compounds or the relation of nucleic acids to cancer fail to consider the possible role of trace elements. Only one discussion considers that chelation may be associated with the cancer process.

This paper will emphasize the hypothesis that the transition element ions, directly, or by metal binding agents, must play an important role both in the etiology and in the present day treatment of cancer. These so called "trace elements" or "minor elements" have long been associated with specific enzymes, or, as in the case of cobalt, with vitamin B12. The consideration of trace metals here is vital, for an understanding of the specific function of trace metals in both enzyme systems and nucleic acid structure may eventually help lead to the elucidation of the entire cancer problem. Evidence for this statement comes from many different sources. These include the nature of the metals that are carcinogenic in action as well as the metal binding structure of carcinogens or their metabolic products. The part played by the metals themselves in the cancer process and the effect of abnormal metals on enzymes also support the thesis. Thus, from the reports in the literature it is possible to gather ample evidence to relate the chelation phenomenon with almost all phases of the carcinogenic process. With only a few exceptions every chemotherapeutic agent effective against human or experimental neoplasms is a chelating agent. This review will attempt to document, and will in the conclusion make suggestions for future corroboration or refutation of, the thesis that chelation plays a vital role in the phenomena which we classify under one heading, cancer.