Patterns of hematological malignancies in Chernobyl clean-up workers (1996-2005)

The question as to whether the incidence of leukemias and malignant lymphomas among the Chernobyl clean-up workers increased in 20 years after the catastrophe is still a point of much controversy. Precise diagnosis of the main forms of hematopoietic malignancies according to FAB classification and new WHO classification and comparison of these data with that in the general population will be helpful in estimating the relative contribution of the radiation factor to the overall incidence of such pathologies.

The data on 218 consecutive cases of malignant diseases of hematopoietic and lymphoid tissues in Chernobyl clean-up workers diagnosed in 1996-2005 are given in comparison with the data of 2697 consecutive patients of general population of the same age group. The morphology and cytochemistry of bone marrow and peripheral blood cells were studied. Immunocytochemical techniques (APAAP, LSAB-AP) and the broad panel of monoclonal antibodies to lineage specific and differentiation antigens of leukocytes were employed for immunophenotyping leukemic cells.

Various types of oncohematological diseases developing 10-20 years after Chernobyl accident were registered in a group of clean-up workers under study including myelodysplastic syndromes (MDS), acute leukemias (ALL and AML), chronic myelogenous leukemia (CML) and other chronic myeloproliferative diseases, chronic lymphocytic leukemia (B-CLL) and other chronic lymphoproliferative diseases of B and T cell origin. MDS percentage among patients of clean-up workers group tended to exceed MDS percentage in the group of patients representing the general population examined at the same period (4.58 vs. 3.70%). Among 34 AML cases, leukemia was preceded by MDS in seven patients. The relative contribution of CML to the total number of clean-up workers with leukemia was higher than the corresponding percentage value in general population examined at the same period (9.17 vs. 6.59%). B-CLL was a predominant form of hematopoietic malignancies in clean-up workers under study (25.68%). Nevertheless, B-CLL percentage in patients of clean-up workers group did not differ significantly from that in the patients of general population. The multiple myeloma percentage (7.79%) in the group of patients belonging to clean-up workers in our study turned out to be twice as much as in the patients of general population (4.0%).

The verified diagnosis of tumors of hematopoietic and lymphoid tissue according to modern classification (EGIL, WHO) could be the prerequisite for further molecular genetic and analytical epidemiology study of leukemias that may be related to Chernobyl NPP accident consequences.