Abstract
To the Editor: Berk and his coauthors from the Polycythemia Vera Study Group reported convincing evidence of a leukemogenic potential of chlorambucil in polycythemia vera (February 19 issue).1 Similar results were reported previously regarding single-agent chemotherapy with other alkylating drugs, such as busulfan in lung cancer2 and dihydroxybusulfan in ovarian carcinoma.3 In the polycythemia vera study, the cases of leukemia that developed in 32P-treated patients were dispersed between the third and the ninth year after the patients' randomization to treatment groups, whereas the majority of cases in chlorambucil-treated patients seemed to appear 2.5 to five years after randomization.In a . . .