Acute myeloid leukemia or one of its variants is being reported with increasing frequency as a second neoplasm in patients being treated for multiple myeloma, Hodgkin's disease, non-Hodgkin's lymphoma and a variety of other primary neoplasms and non-neoplastic diseases. Although many of these patients were treated with both chemotherapy and radiotherapy, many received no radiotherapy at all. Drugs most frequently implicated in the causation of acute leukemia and other second neoplasms are the alkylating agents, procarbazine and the nitrosoureas. The frequency of this syndrome varies from less than 1 per cent to 7 per cent in many reported series of patients. There could develop a reluctance to use cytotoxic agents to treat malignant neoplasms for fear of inducing acute leukemia. Although one has to consider this complication, one should not, however, withhold these drugs from a patient with a neoplasm or other potentially fatal disease in whom such therapy is the treatment of choice. We seem to be faced with the paradox that patients benefiting most from chemotherapy may be at highest risk of suffering its undesirable consequences. Although the risk of leukemogenesis or carcinogenesis in man may be small, these drugs should be used with caution in patients with indolent non-neoplastic diseases such as rheumatoid arthritis.
