The effect of 2-h infusion of 2-chlorodeoxyadenosine (cladribine) with prednisone in previously untreated B-cell chronic lymphocytic leukaemia.

2-Chlorodeoxyadenosine (2-CdA) is a new antimetabolite chemotherapeutic agent active in indolent lymphoid malignancies. In this retrospective study, 69 previously untreated patients with B-cell chronic lymphocytic leukaemia (B-CLL) were treated with 2-CdA administered at a dose of 0.12 mg/kg daily in 2-h intravenous infusion for 5 consecutive days. 45 patients also received prednisone 30 mg/m2 orally each day for 5 days starting with 2-CdA courses. Patients were given 2-6 courses (mean 4.6) of 2-CdA repeated usually at monthly intervals. If a complete response was achieved, no further 2-CdA courses were administered. Guidelines for response were those developed by the NCI Sponsored Working Group. Complete response (CR) was achieved in 26 (38%) and partial response (PR) in 27 (39%) cases, giving an overall response rate of 77%. 16 patients (23%) did not respond to 2-CdA. In the subgroup of 45 patients receiving 2-CdA with prednisone, CR was obtained in 15 (33%) and PR in 20 (44%) patients giving an overall response rate of 78%. CR was achieved in 11 (46%) out of 24 patients treated only with 2-CdA and in 7 cases (29%) PR was observed, giving an objective response rate of 75%. The differences between both subgroups were not statistically significant. However, we observed a relationship between the response and the number of courses of 2-CdA given in patients receiving and those not receiving prednisone. In the subgroup receiving 2-CdA with prednisone, an earlier response to 2-CdA was observed. In this group a response was achieved in 9 (20%) patients after two courses of 2-CdA and in 18 (40%) after four courses. In the subgroup receiving only 2-CdA, 17 (71%) responses were obtained after six cycles.

The effect of isolated leukaemic blasts on platelet aggregation.

The effect of blastic cells isolated by Böyum's method from the blood of 20 nontreated patients with acute myelogenous leukaemia on normal platelet aggregation has been studied. The isolated blasts in concentration of 2,000/microliter and higher, inhibit normal platelet aggregation induced by ADP or collagen, but have no influence on aggregation initiated by epinephrine. This effect is unaffected by the presence of metabolic poisons or by the disruption of the blastic cell membrane. Our results seem to exclude interference of blastic cells with platelet prostaglandin biosynthesis. In patients with acute leukaemia and an increased leukocyte count the preparation of platelet suspension free of blastic cells is not possible, even by the albumin gradient method or by gel filtration. The leukaemic blast content in platelet-rich suspensions may account for the variations in the aggregation behaviour which are found in these patients. The influence of blastic cells may be an important factor in the bleeding tendency in myelogenous leukaemia

2-Chlorodeoxyadenosine (cladribine)-related eosinophilia in patients with lymphoproliferative diseases.

Eosinophilia and allergic skin reactions are uncommon events after 2-chlorodoxyadenosine (2-CdA, cladribine) administration. A multicentre retrospective analysis of eosinophilia in 360 patients treated with 2-CdA for lymphoid malignancies has been made. B-cell chronic lymphocytic leukaemia (B-CLL) was diagnosed in 153, hairy cell leukaemia (HCL) in 68, low-grade non-Hodgkin's lymphoma (LGNHL) in 119, high-grade NHL in 2 and Waldenstrom's macroglobulinaemia (WM) in 18 patients. 2-CdA was administered at a dose 0.12 mg/kg/d in 2-h intravenous infusion for 5 consecutive d. The courses were repeated monthly. Patients with HCL received 1 cycle of 2-CdA, with NHL 2-6 (mean 3.5) cycles and with B-CLL 3-6 (mean 5) cycles. Twenty patients (5.5%), including 5 with HCL, 6 with LGNHL, 7 with B-CLL and 2 with WM, developed peripheral blood eosinophilia. The mean values of absolute eosinophil count were 0.78x10(9)/l (0.58-1.06x10(9)/l), 0.71x10(9)/l (0.52-1.3x10(9)/l), 85 (0.56-1.82x10(9)/l) and 0.75 (0.74-0.76x10(9)/l), respectively. Eosinophilia occurred in 13 patients after 1 course, in 4 after 2 courses, and in 5 after > or =3 courses of the therapy. In 17 cases it resolved spontaneously. Allergic skin lesions with pruritus were noticed in 3 patients simultaneously with an increase in eosinophil count. All of them required antihistaminic drugs and/or corticosteroids. One patient with B-CLL experienced repeated episodes of eosinophilia. The highest incidence of 2-CdA-induced eosinophilia was noticed in patients with MW (11.1%) and HCL (7.4%) who received only 1 cycle of this drug and entered a complete remission. This side effect was less frequently observed in LGNHL and B-CLL, i.e. in 5.0% and 4.6% of cases, respectively. The mechanism of 2-CdA-induced eosinophilia is not clear. It has been postulated that massive tumour cell lysis may trigger a release of IL-5 and probably other cytokines. The allergic mechanism of 2-CdA-induced eosinophilia is also possible, especially in patients with simultaneous skin reactions.