The initial therapies of choice are either cladribine (2-chlorodeoxyadenosine, 2-CdA) or pentostatin.[1,2] These drugs have comparable response rates but have not been compared in phase III trials. Cladribine is administered as a one-time continuous infusion or series of subcutaneous injections and is associated with a high rate of febrile neutropenia.[3,4,5,6] Rarely, more than one course of treatment is required to induce a desirable response. Treatment should be discontinued once complete remission or stable partial remission with normalization of peripheral blood counts is reached. The presence of residual disease may be predictive of relapse but does not seem to affect survival.[5,7]
The role of consolidation or maintenance therapy in preventing relapse or progression of the disease following treatment with purine analogs has not been evaluated and remains unproven. Pentostatin is administered intermittently for a longer treatment duration but may result in a lower incidence of febrile complications.[8,9] While most patients remain disease free 10 years after treatment with these purine analogs, no patient has been followed long enough to assess cure.[10,11] Both nucleoside analogs cause profound suppression of CD4 counts, which may last for a year, and a potential increased risk of second malignancies has been reported.[5,12]
There are several types of plasma cell neoplasms. These diseases are all associated with a monoclonal (or myeloma) protein (M protein). They include monoclonal gammopathy of undetermined significance (MGUS), isolated plasmacytoma of the bone, extramedullary plasmacytoma, and multiple myeloma.
(Refer to the Lymphoplasmacytic Lymphoma (Waldenström Macroglobulinemia) section in the PDQ summary on Adult Non-Hodgkin Lymphoma Treatment for more information.)
Incidence and Mortality
A study of 3,104 survivors of hairy cell leukemia from the SEER database showed an increased risk of second cancers (standardized incidence ratio, 1.24; 95% CI, 1.11-1.37), especially for Hodgkin and non-Hodgkin lymphomas. The increased risk for second cancers was seen even in the 2 decades prior to the introduction of purine nucleosides. With the use of cladribine, an increased risk of second malignancies is possible among patients with hairy cell leukemia (observed to expected ratio of about 1.8 in several series after 6 years).[5,12] Several series using pentostatin did not report an increased risk of second malignancies.[8,10,14] For a few patients, such as those with severe thrombocytopenia, splenectomy might be considered. After splenectomy, 50% of patients will require no additional therapy, and long-term survivors are common. Therapy with interferon-alpha is another treatment option, especially for patients with intercurrent infection.[9,16]