Studies in hairy cell leukemia 25
results from administration of either pentostatin or
Table IV. Conclusions from long-term studies in HCL.
cladribine [21,22]. The frequency of febrile neutro-
Enormous progress with prolonged survival, but about 40%
penia is less when therapy involves interrupted
will relapse
administration of pentostatin [3]. The administration Substantial evidence of residual disease despite achieving a
of either reduced doses of pentostatin or prolonga-
complete remission
tion of the period between treatments are less likely
Need for clinical research to improve outcome with combination
therapies and to search for new agents
to result in a prolonged myelosuppression related to
Need for consistency in treatment with optimal agents, doses,
therapy. Although the protracted administration of
and duration of therapy
low dose pentostatin may require more visits to the
outpatient clinic, this may be better tolerated in
HCL, hairy cell leukemia.
patients with severe compromise of bone marrow
function. Zinzani et al. did observe that weekly continued study to define the optimal therapeutic
cladribine was associated with less myelosuppression regimen. Duration of therapy, optimal dose and
than those reported on the 7-day intravenous schedule of drug administration, and the need for
schedule [16]. For patients with an active infection additional biologic or immunologic agents should be
who require therapy or in those with severe compro- investigated. In those patients with resistant or
mise of bone marrow function, dose modification at relapsed disease, we need to explore the new agents
initial therapy seems prudent. Robak published a and the targeted immunotoxin conjugates. Some of
prospectively randomized trial with cladribine, and the newer therapies that have been useful for resistant
found that weekly administration was equally effec- chronic lymphocytic leukemia are worthy of explora-
tive but not less toxic than the 5-day schedule [20]. tion in this disease. Some of these newer agents may
Because infection represents a practical concern not share the toxicity on immune effector cells or
for patients with HCL, optimizing therapy by normal bone marrow that is observed with the purine
lessening initial myelosuppression is important. nucleoside analogs.
This will be particularly true for patients requiring Finally, there is a need for consistent recommen-
therapy despite having an active infection. dations for therapy in this disease that are based upon
Careful assessment for the risk of secondary careful clinical trials. In an effort to provide access to
malignancies reveals either a slight increase in the this information, the Hairy Cell Leukemia Consor-
risk of a second malignancy or no increase related to tium was established in 2008. Their new web site
treatment [8,15,17,18]. Patients who are treated with may be useful for the physicians and the patients
purine analogs will need long-term follow-up be- (www.hairycell.org). The rarity of this disease re-
cause the potential for myelodysplasia has not been quires that we communicate our findings to a broad
completely evaluated. This is particularly important audience of hematologists and their patients.
for patients requiring repeated exposure to these Although tremendous progress has been made in
agents. Treatment beyond that required to achieve a the management of these patients, we still need to
complete hematological remission in an attempt to collaborate on critical questions that are unanswered.
eradicate the minimal residual disease is another
fruitful area for continued clinical research. Patients Declaration of interest: The authors report no
who have a complete hematologic remission are conflicts of interest. The authors alone are respon-
frequently found to have minimal residual disease by sible for the content and writing of the article.
immunohistochemical and immunophenotypic stu-
dies. The combined use of rituximab following a
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