The data presented by Kaplan and colleagues in the current issue of Cancer do not appear to be sufficiently mature to suggest the absence of an association between agents used in the treatment of breast carcinoma and the development of secondary leukemia. The updating of these data over an adequate follow-up period may prove critical to the conclusions that are drawn. In addition, stratification of data according to accepted risk factors for secondary leukemia is warranted.

See pages 1529–36.