Non-Hodgkin's lymphoma: the evolving role of purine analogues

Current status of older and new purine nucleoside analogues in the treatment of lymphoproliferative diseases

For the past few years more and more new cytotoxic agents active in the treatment of hematological malignancies have been synthesized and become available for either in vitro studies or clinical trials. Among them the class of antineoplastic drugs belonging to the purine nucleoside analogues group (PNAs) plays an important role. Three of them: pentostatin (DCF), cladribine (2-CdA) and fludarabine (FA) were approved by Food and Drug Administration (FDA) for the treatment of hematological malignancies. Recently three novel PNAs: clofarabine (CAFdA), nelarabine (ara-G) and forodesine (immucillin H, BCX-1777) have been synthesized and introduced into preclinical studies and clinical trials. These agents seem to be useful mainly for the treatment of human T-cell proliferative disorders and they are currently undergoing clinical trials in lymphoid malignancies. However, there are also several studies suggesting the role of these drugs in B-cell malignancies. This review will summarize current knowledge concerning the mechanism of action, pharmacologic properties, clinical activity and toxicity of PNAs accepted for use in clinical practice, as well as new agents available for clinical trials.

Recent progress in the management of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a clonal disease characterized by proliferation and accumulation of small CD5-positive B cells. More than 50% of patients are asymptomatic at diagnosis and usually require no treatment. However, treatment is needed in the advanced and progressive disease. Chlorambucil with or without steroids has been the drug of choice for many years in previously untreated patients with CLL. The purine nucleoside analogs (PNAs), fludarabine (FA), cladribine (2-CdA-chlorodeoxyadenosine) and pentostatin (DCF, 2'-deoxycoformycin) also have been introduced for treatment of CLL. Significantly higher overall response (OR) and complete response (CR) and longer progression free survival (PFS) in patients with CLL treated with FA or 2-CdA have been confirmed in randomized, multicenter trials and more recently in meta-analysis. However, the median survival time did not differ between patients treated with PNA and alkylating agents. Combination therapies with PNAs and cyclophosphamide and especially with cyclophosphamide and rituximab are more active than monotherapy in terms of OR, CR and PFS. Several reports have shown significant activity of alemtuzumab in previously untreated and pretreated patients even when refractory to FA. Alemtuzumab also can be used in CLL as a preparative regimen before stem cell transplantation (SCT) and to eliminate minimal residual disease (MRD). Recently, several new agents have shown promise in treating CLL, including new monoclonal antibodies, agents targeting bcl-2 family of proteins, antisense oligonucleotides and other agents. Moreover, autologous and allogenic hematopoietic cell transplantations are increasingly considered for treatment of patients with CLL. In this review current therapeutic strategies in CLL are presented.

Recognizing hyperviscosity syndrome in patients with Waldenstrom macroglobulinemia

Hyperviscosity syndrome can develop in patients with plasma cell dyscrasias, particularly Waldenstrom macroglobulinemia (WM). Occurring in 10%-30% of patients with hyperviscosity syndrome, WM is an uncommon B-cell proliferative disorder characterized by bone marrow infiltration and production of monoclonal immunoglobulin M. The elevated blood viscosity in WM is the result of increased circulating serum immunoglobulin M. Because hyperviscosity syndrome can be lethal, it must be recognized and managed early. Hyperviscosity syndrome has a triad presentation: vision changes, neurologic abnormalities, and bleeding. Treatment includes hydration with diuresis, plasmapheresis, and control of the underlying disease. The current treatment for WM is chemotherapy (i.e., alkylating agents and nucleoside analogs) and the monoclonal antibody rituximab. Although hyperviscosity syndrome is not one of the most common conditions, when it does occur, oncology nurses play a critical role in patients' assessment and care.

Purine Analogue Combinations for Indolent Lymphomas

Indolent lymphomas are a group of lymphoid malignancies with differing patterns of behavior and responses to treatment. The progress in treating patients with hairy cell leukemia (HCL) using nucleoside analogues can be used as a model for other indolent B-lymphoproliferative disorders, such as follicular lymphoma. Recent advancements in therapeutic options available for these patients include combination therapy with agents that have differing mechanisms of action and non-overlapping toxicity. It has been shown that patients who are candidates for aggressive therapy might receive benefit, including disease-free survival and overall survival, from combination purine analogue therapy. Using these more aggressive therapeutic approaches earlier in the disease course and as maintenance therapy may further enhance outcomes. With the advent of these new therapies along with the molecular evaluation of these regimens, we may be nearing the time where the goal for more advanced indolent lymphoma will be to achieve a cure.

Costs of chemotherapy for indolent follicular non-Hodgkin's lymphoma in the UK: an observational study

Non-Hodgkin's lymphoma (NHL) is the sixth most common cancer in the United Kingdom (UK). This analysis assessed the health service costs of patients receiving chemotherapy for indolent follicular NHL based on a retrospective analysis of patient records in the UK. Each patient was followed up for a period of 3 years or until death. The analysis included 181 patients, who received a total of 187 treatment periods. Costs were estimated from the perspective of the UK National Health Service. The study found the cost of providing treatment with CHOP (cyclophosphamide, doxorubicin, vincristine, prednisolone) or fludarabine to patients with indolent follicular NHL to be lower than previously reported.

Early-onset autoimmune hemolytic anemia after cladribine therapy for Waldenström's macroglobulinemia

BACKGROUND

Purine nucleoside analogs are a class of antineoplastic drugs with potent lymphotoxicity against T and B lymphocytes, causing prolonged lymphopenia and linked to delayed immune complications such as opportunistic infections and more recently autoimmune hemolytic anemia (AIHA), seen mostly in patients with chronic lymphocytic leukemia (CLL). A characteristic temporal relation between fludarabine therapy and the appearance of a warm-reactive immunoglobulin G (IgG)-mediated AIHA in patients with CLL has been observed and, in some, the AIHA has been fatal. Whether both fludarabine and cladribine cause AIHA is uncertain because AIHA is commonly seen in patients with CLL without the use of these drugs. In contrast, AIHA is encountered in Waldenström's macroglobulinemia (WM) much less frequently, and the autoantibody is usually cold-reactive and IgM-mediated. In a few reported cases of AIHA arising in patients with WM after cladribine therapy, there was a latency of 24 to 60 months between therapy and the onset of AIHA, three of which were warm-reactive and IgG-mediated.

CASE REPORT

A warm-reacting IgG red cell autoantibody and evidence of hemolysis detected 1 month after completing cladribine therapy for WM, with warm antibody AIHA developing 4 months later, are described.

CONCLUSIONS

Cladribine, like fludarabine, is possibly able to produce this complication during or early after therapy. Because the use of purine analogs is becoming increasingly common, it is important to have an awareness of the complications that can arise during and after treatment. Further observations of warm AIHA during cladribine therapy are needed to establish it as a distinct complication.

Therapy of Chronic Lymphocytic Leukaemia with Purine Nucleoside Analogues

Chronic lymphocytic leukaemia (CLL) is a neoplastic disease of unknown aetiology characterised by an absolute lymphocytosis in peripheral blood and bone marrow. The disease is diagnosed most commonly in the elderly with the median age at diagnosis being about 65 years. The purine nucleoside analogues (PNAs) fludarabine, cladribine (2-chlorodeoxyadenosine) and pentostatin (2'-deoxycoformycin) are highly active in CLL, both in previously treated and in refractory or relapsed patients. These three agents share similar chemical structures and mechanisms of action such as induction of apoptosis. However, they also exhibit significant differences, especially in their interactions with enzymes involved in adenosine and deoxyadenosine metabolism. Recent randomised studies suggest that fludarabine and cladribine have similar activity in CLL. However, clinical observations indicate the existence of cross-resistance between fludarabine and cladribine. Patients who received PNAs as their initial therapy and achieved long-lasting response can be successfully retreated with the same agent. PNAs administered in combination with other chemotherapeutic agents and/or monoclonal antibodies may produce higher response rates, including complete response (CR) or molecular CR, compared with PNAs alone or other treatment regimens. Management decisions are more difficult in elderly patients because of the apparent increase in toxicity of PNAs in this population. In elderly patients, we recommend chlorambucil as the first-line treatment, with PNAs in lower doses in refractory or relapsed patients. Myelosuppression and infections, including opportunistic varieties, are the most frequent adverse effects in patients with CLL treated with PNAs. Therefore, some investigators recommend routine antibacterial and antiviral prophylaxis during and after PNA treatment. This review presents current results and treatment strategies with the use of PNAs in CLL, especially in elderly patients.