Long-term cytogenetic effects of antineoplastic treatment in relation to secondary leukemia

Chromosome translocations are consistently present in leukemias and lymphomas and are likely to represent primary events in the development of these neoplasias. A study of conditions that predispose to leukemia could shed some light on the origin of these translocations and therefore help in clarifying their exact role in the process of neoplastic transformation. Based on this assumption, we studied a group of individuals treated with radiochemotherapy for previous lymphoma and who were at increased risk of developing a secondary leukemia. The group comprised 14 Hodgkin's disease patients, 11 non-Hodgkin's lymphoma patients, and 13 controls. The patients were in remission and had been off therapy for at least 6 months. Chromosomes were studied from phytohemagglutinin (PHA)-stimulated peripheral lymphocytes and from bone marrow cells by the direct method and after short-term cultures (72 hours). The latter were also exposed to 5-bromodeoxyuridine (BrdU). Metaphases were scored for chromosome breaks, gaps, and other rearrangements. The percentage of gaps and breaks was significantly higher in patients than in controls. The difference was induced by BrdU and was apparent in bone marrow cells, but not in peripheral lymphocytes. We conclude that individuals exposed to the action of mutagenic agents (radiochemotherapy) have an increased chromosome instability that could be related to their increased risk of developing a secondary leukemia.