The association between systemically administered radioisotopes and subsequent malignant disease.
There is a long history recording the association of x radiation and the subsequent development of malignant tumors. For systematically administered isotopes this came into prominence when Martland discovered the association between cancer, particularly of the bone, and ingestion of radioactive isotopes by radium dial painters. This association was amplified by the development of cancer in patients given thorotrast as a contrast medium for diagnostic radiologic examination. Acute leukemia was reported 30 years ago in patients with polycythemia vera treated with 32P. Acute leukemia also occurs in patients with polycythemia vera treated only with phlebotomy or drugs. A controlled study is now underway to provide a more definite answer to question what is the incidence of acute leukemia in patients with polycythemia vera treated by phlebotomy alone, chlorambucil, or 32P. 131I for the treatment of hyperthyroidism probably does not induce cancer, but in the doses used for thyroid cancer there was an increased incidence of neoplasms (12/200 in one study). This was higher than the expected incidence of neoplasms. The doses of radioactive isotopes used currently for diagnostic purposes have not induced cancer, but it is difficult and probably impossible to verify this with absolute certainty.