PROGNOSIS OF THE COURSE OF CHORNOBYL-ORIGINATED ACUTE LYMPHOBLASTIC LEUKEMIA IN CHILDREN IN UKRAINE DEPENDING ON THE REASON OF STANDARD CHEMOTHERAPY INTERRUPTION. / PROGNOZ PEREBIGU GOSTRYKh LIMFOBLASTNYKh LEY̆KEMIY̆ ChORNOBYL'S'KOGO POKhODZhENNIa U DITEY̆ UKRAÏNY ZALEZhNO VID PRYChYN PERERV PRY PROVEDENNI STANDARTNOÏ KhIMIOTERAPIÏ.

OBJECTIVE: Estimation of the bone marrow haemopoietic status depending on the reasons and duration of breaks in a standard chemotherapy (BFM-ALL protocol) to predict the course of acute lymphoblastic leukemia (ALL) in chil- dren exposed to low doses of ionizing radiation after the Chornobyl accident. MATERIALS AND METHODS: The ALL patients (n = 34) were examined within 5 stages of a program chemotherapy. The clinical symptoms, hemogram and myelogram data were analyzed. The radiation dose on bone marrow, initial leuko- cyte count, variants and prognosis of ALL course were accounted. Days of the stopped chemotherapy, type and fre- quency of complications (septic processes, febrile neutropenia, toxic hepatitis, granulocytopenia degree), and the prognosis of disease course (child living status, i.e. alive or died) were estimated. RESULTS: There were abnormal differentiation processes and high percentage of lymphoblasts (86.2 ± 3.3) % in bone marrow in the 1st acute period. Hematological remission was established in all patients on the 33rd day of chemothe- rapy. In a half of cases the haematopoietic recovery occurred by a granulocyte-monocyte type. One third of patients presenting an erythroid type of haemopoiesis died later. The inverse correlation was found between the number of myelocaryocytes and disease prognosis (rs = -0.49). Breaks in chemotherapy for various reasons were recorded. The number of patients with granulocytopenia was greater at the phase 1 and 2 of protocol I and protocol M application, coinciding with a higher incidence of complications. An inverse correlations between the prediction of ALL course and sum of days of breaks between the protocol M and phase 1 of protocol II (rs = -0.56), as well as the duration of the phase 2 of protocol II (rs = -0.62) were found. The radiation dose on bone marrow was (5.37 ± 1.23) mSv. No relationship was found between the radiation doses, ALL variants and disease course. CONCLUSIONS: Prognosis of ALL course in children depends on the type of haemopoietic recovery and reasons of breaks in a standard chemotherapy. Interaction between the haemopoiesis functioning and microenvironment and that of their regulation are the key mechanisms of above-mentioned abnormalities, which is the basis for further research.