16 E. Huynh et al.
light microscopy. Ellison et al. evaluated minimal should still be considered the standard and remains
residual disease (MRD) using immunohistochemical the schedule currently used to treat patients with
techniques with the antibodies L26 (CD20) and HCL at Scripps Clinic. Patients who relapse after
DBA.44. They examined 154 bone marrow biopsies purine analogue therapy, whether it be with cladri-
performed between three and 25 months after one bine or pentostatin, can be effectively retreated with
course of cladribine. Fifty percent of the biopsies cladribine with an expected CR rate of 70–80%.
stained positively for L26 and/or DBA.44 in five or Patients with HCL may suffer from complications of
more cells with morphologic features of hairy cells. recurrent infections and second malignancies. Fil-
MRD was usually less than 1% of the total cellular grastim has not been shown to be clinically effective
population. The level of MRD remained stable over in reducing the rates of febrile illness or infections
the 25 months of the follow-up [24]. related to cladribine therapy and is, therefore, not
Wheaton et al. examined MRD in 39 patients in routinely recommended as adjunctive therapy. MRD
complete remission after a single treatment of can be found in up to 50% of patients treated with a
cladribine. Three of the six patients (50%) who single course of cladribine and is thought to predict
were detected with MRD after therapy relapsed, for future relapse. Studies in combination with
whereas only one of 25 patients (4%) without MRD rituximab show that elimination of MRD may be
relapsed (p¼0.016). These data suggest that the beneficial. Long-term follow-up, up to 20 years,
presence of MRD might predict for relapse in demonstrates that cladribine could be potentially
patients treated with cladribine [25]. curative for some patients with HCL.
To improve on the initial response to purine
analogues, Ravandi et al. treated 13 patients with Declaration of interest: The authors report no
cladrdibine (0.6 mg/m
2
given intravenously over 2 h conflicts of interest. The authors alone are respon-
daily for 5 days) followed by rituximab (375 mg/m
2
sible for the content and writing of the paper.
intravenously weekly for 8 weeks). MRD was
assessed using consensus primer polymerase chain
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