Hairy cell leukemia. An alternative method for the detection of minimal residual disease using flow cytometry.

In patients with hairy cell leukemia (HCL) who received chemotherapeutic treatment and achieved complete remission (CR), minimal residual disease (MRD) can be detected in bone marrow biopsies using immunohistochemical (IHC) techniques. in this study, we investigated the value of flow cytometry (FCM) and IHC to detect MRD and to establish whether MRD+ could predict relapse. A total of 15 HCL patients in CR were studied. Samples of bone marrow (BM) and peripheral blood (PB) were processed by FCM with triple staining of the following monoclonal antibodies (mAbs): CD20, CD22, CD11c, CD103, CD25, anti-Kappa and anti-lambda light chains. Reference values were obtained from normal samples of peripheral blood and bone marrow. FCM detected MRD in 64% of the patients. BM samples were more demonstrative than peripheral blood for MRD detection in HCL. IHC was performed in paraffin-embedded BM biopsies using CD20 and DBA44 mAbs. MRD+ was detected in 46% of patients. Although not statistically significant, FCM appeared more sensitive compared with IHC. Detection of MRD by either of these methods in our series did not predict hematological relapse. The results show that FCM is a useful alternative method to detect MRD in HCL and that a longer follow-up is required to establish the predictive outcome of MRD+ patients.