Molecular evaluation of clonal remission in hairy cell leukemia patients treated with 2-chlorodeoxyadenosine

Several reports have documented complete and long-lasting remissions in hairy cell leukemia (HCL) patients after a single one-week course of 0.1 mg/kg/d of 2-Chlorodeoxyadenosine (2-CdA) administered by intravenous infusion. In these studies the evaluation of the clinical response was based on physical examination, blood cell counts, as well as cytochemical and immunological detection of residual leukemic cells. Since HCL is a chronic lymphoproliferative disorder characterized by the expansion of monoclonal B cells, analysis of the configuration of the immunoglobulin gene regions represents a valuable tool towards a more accurate monitoring of treatment response. We hereby describe the molecular assessment of the neoplastic clone in six HCL patients treated with 2-CdA; in five of them a disappearance of the rearranged bands could be documented in bone marrow cells aspirated between 2 and 21 months after a single course of continuous infusion 2-CdA. The last HCL case analyzed, revealed molecular persistence of the neoplastic clone. In all cases but one, the molecular evaluation was in agreement with the definition of clinical response based on conventional analysis. This study demonstrates that HCL patients treated with 2-CdA show a high incidence of molecularly-defined complete remissions, the likelihood of which is much greater than for patients treated with Interferon alpha.