Followup study on the mortality and the development of leukemia in 44 pancytopenic patients with chronic exposure to benzene.

A followup study of 2-17 yr was performed on 44 pancytopenic patients with benzene exposure. They had been subjected to high concentrations of benzene (150-650 ppm) in adhesives for 4 mo to 15 yr. The benzene content of the adhesives varied between 9% and 88%, (average 50%). Complete remission was seen in 23 patients and fatal outcome due to complications of pancytopenia was observed in 14 pancytopenic patients. In 6 pancytopenic patients leukemia developed after a period of 6 mo to 6 years. In a patient with complete remission fatal myeloid metaplasia occurred. The mean age and the duration of exposure of 21 patients with overall fatal outcome were significantly higher than those of 23 patients with complete remission. However, with the exception of mean values of neutrophils, the findings in peripheral blood, including the levels of HbF and A2, could not be correlated with the outcome of benzeneinduced pancytopenia. On the other hand, in one patient a very low level of HbA2 and a high level of HbF were already evident during the pancytopenic period, whereas preleukemia developed 9 mo later. This observation suggests that low levels of HbA2 with or without high levels of HbF during pancytopenia may be a sign of leukemia. Moreover, there was a clear relationship between the type of bone marrow cellularity and the outcome of pancytopenic patients. The development of leukemia in 6 of 44 pancytopenic patients with chronic exposure to benzene is further evidence for the leukemogenic effect of benzene in man.