The degree of bone marrow infiltration in patients with hairy cell leukemia treated with splenectomy compatible with long-term hematological remission

To determine the degree of bone marrow infiltration with hairy cells which is compatible with long-term hematological remission in patients treated with splenectomy, we have investigated 7 patients surviving in hematological remission 61 to 255 months (median 184 months) after splenectomy. As hematological remission has been considered absence of hairy cells (HCs) in the peripheral blood, normalization of peripheral blood cell counts (hemoglobin 120 g/l, white cell count 4.0 x 10(9)/l, absolute granulocyte count 1.5 x 10(9)/l, platelet count 100 x 10(9)/l) and absence of lymfadenopathy and any other activity of the disease. For detection of HCs a very sensitive method of immunostaining with monoclonal antibody DBA.44 in our own modification has been used. Low values of sIL-2R which is considered to be a non invasive marker of tumor burden and activity in HCL were in agreement with the opinion that the bone marrow was the only locality of tumor involvement in splenectomized patients. Infiltration up to 20% with HCs (range 4% to 20%,median 10%) was found to be compatible with long-term hematological remission and long-term overall survival. Patient (No 1) with 30% infiltration of bone marrow with HCs, still normal peripheral blood cell counts, but a very high level of sIL-2R represents extraordinary finding which has been discussed in details.