Lack of effect of 2-chlorodeoxyadenosine therapy in patients with chronic lymphocytic leukemia refractory to fludarabine therapy

Chronic lymphocytic leukemia: present status

Chronic lymphocytic leukemia (CLL) is the form of leukemia which occurs most frequently in Western countries. Its etiology is unknown, and no relationship with viruses or genes has been demonstrated. Epidemiological data suggest that genetic and ambiental factors might be of some significance. Clinical features of CLL are due to the accumulation of leukemic cells in bone marrow and lymphoid organs as well as the immune disturbances that accompany the disease. The prognosis of patients with CLL varies. Treatment is usually indicated by the risk of the individual patient, which is clearly reflected by the stage of the disease. In the early stage (Binet A, Rai O) it is reasonable to defer therapy until disease progression is observed. By contrast, because their median survival is less than five years, patients with more advanced stages require therapy. For almost 50 years, no major advances in the management of CLL, which has revolved around the use of alkylating agents, have been made. In recent years, the therapeutic approach in patients with CLL has changed as a result of the introduction of combination chemotherapy regimens and, in particular, purine analogues. The latter are already the treatment of choice for patients not responding to standard therapies, and their role as front-line therapy is being investigated. Bone marrow transplants are also being increasingly used. It is to be hoped that in years to come the outcome of patients with CLL will be improved by these advances.

Treatment of Waldenstrom's macroglobulinemia resistant to standard therapy with 2-chlorodeoxyadenosine: identification of prognostic factors

BACKGROUND

Few effective treatments are available for patients with Waldenstrom's macroglobulinemia that is resistant to standard therapies. We assessed the activity of 2-chlorodeoxyadenosine (2CdA) in patients with resistant macroglobulinemia in order to identify those most likely to benefit.

PATIENTS AND METHODS

2-chlorodeoxyadenosine was given to 46 consecutive patients with Waldenstrom's macroglobulinemia resistant to a combination of an alkylating agent and a glucocorticoid. Two courses were administered to outpatients at a dose of 0.1 mg/kg body weight per day for a 7-day continuous infusion using a portable pump through a central venous catheter. Responding patients were followed without further therapy.

RESULTS

Twenty of 46 patients responded to 2CdA therapy (43%; 95 CI; 29 to 60%) with a significantly higher frequency of benefit among patients with disease relapsing off therapy (78%) or with primary resistant disease within the first year (57%) than in those with later phases of disease (22%). The median survival after treatment was 28 months and the median progression-free survival of responding patients was 12 months. The longest survival was measured in patients with primary refractory disease (projected median 36 months) and the shortest in those with disease in refractory relapse (median 13 months).

CONCLUSION

2-Chlorodeoxyadenosine is active against macroglobulinemic lymphoma resistant to standard regimens and most effective in patients with disease relapsing off treatment or during the first year of primary refractory disease. Little benefit was observed among patients with later phases of resistant disease who should receive alternative treatments.

Apoptosis induction with three nucleoside analogs on freshly isolated B-chronic lymphocytic leukemia cells

The cytotoxic effects and the induction of programmed cell death (apoptosis) by Fludarabine (FLU), 2-chlorodeoxyadenosine (2-CdA), and deoxycoformycin (DCF) with/without alpha-interferon (alpha-IFN) were evaluated in vitro against freshly isolated B-chronic lymphocytic leukemia (B-CLL) cells. Cytotoxicity was evaluated according to the soluble tetrazolium/formazan assay. Regarding the cytotoxicity, FLU, 2-CdA, and DCF showed a mean antitumor activity of 45% +/- 3.39 (mean +/- S.D.), 55% +/- 4.72, and 20% +/- 3.16, respectively. alpha-IFN alone showed a mean cytotoxic activity of 10% +/- 2.72. The cytotoxicity of these purine analogues in combination with alpha-IFN was 52% +/- 2.97, 75% +/- 3.41, and 26% +/- 7.09, respectively. We observed a statistically significant increase of cytotoxicity compared to controls in FLU alone (P < 0.05), 2-CdA (P < 0.05), and their combination with alpha-IFN (P < 0.05). Apoptosis was evaluated by electrophoresis gel of DNA oligonucleosomal fragments and by a cytofluorimetric method. Only FLU and 2-CdA activated the apoptosis and DCF showed a minor apoptotic pathway amount. These apoptosis data were confirmed by both gel electrophoresis of DNA and by propidium iodide cytofluorimetric method. FLU and 2-CdA show activity in B-CLL cells by direct cytotoxic action and the induction of cell death by apoptosis; in the future, it would be interesting to utilize these in vitro assays in monitoring chemosensitivity and predicting response for the clinical use.