Therapy-related preleukemic syndrome.

Eight patients developed the preleukemic syndrome after having been exposed to cytotoxic drugs for other primary diseases. All eight subsequently developed acute nonlymphocytic leukemia (ANLL). Survival following the onset of the preleukemic syndrome ranged from 5-34 months with a median of 11 months. Once overt leukemia developed median survival was three months. No patient responded to conventional antileukemic therapy. A higher incidence of chromosomal abnormalities was noted in bone marrow cells of this group (five of six) when compared with a larger group of preleukemic patients not known to have been exposed to mutagens (four of 21). In addition, two patients had second chromosome studies after overt leukemia developed and there was no evidence of cytogenetic clonal evolution. The clinical course and cytogenetic data in these patients attest to the relevance of our criteria in identifying the preleukemic syndrome and suggest that the leukemic clone was fully established during the preleukemic phase. Thus, patients previously exposed to cytotoxic therapy who develop the preleukemic syndrome may be viewed as having early leukemia.