Minimal residual disease may predict bone marrow relapse in patients with hairy cell leukemia treated with...

Minimal residual disease (MRD) can be detected in bone marrow core biopsies of patients with hairy cell leukemia (HCL) after treatment with 2-chlorodeoxyadenosine (2-CdA) using immunohistochemical (IHC) techniques. The purpose of this study was to determine whether the presence of MRD predicts bone marrow relapse. We studied paraffin-embedded bone marrow core biopsies from 39 patients with HCL in complete remission (CR) 3 months after a single cycle of 2-CdA. Biopsies performed 3 months posttherapy and annually thereafter were examined by routine hematoxylin and eosin (H&E) staining and IHC using the monoclonal antibodies (MoAbs) anti-CD45RO, anti-CD20, and DBA.44. At 3 months after therapy, 5 of 39 (13%) patients had MRD detectable by IHC that was not evident by routine H&E staining. Two of the five patients (40%) with MRD at 3 months have relapsed, whereas only 2 of 27 (7%) patients with no MRD and at least 1 year of follow up relapsed (P = .11). Over the 3-year follow-up period, two additional patients developed MRD. Overall, three of six (50%) patients with MRD detected at any time after therapy have relapsed, whereas only 1 of 25 (4%) patients without MRD has relapsed (P = .016). These data suggest that the presence of MRD after treatment with 2-CdA may predict relapse.