High complete remission rate from 2-chloro-2'-deoxyadenosine in previously treated patients with B-cell chronic lymphocytic leukemia: response predicted by rapid decrease of blood lymphocyte count.
PURPOSE This study attempted to characterize the response of previously treated patients with B-cell chronic lymphocytic leukemia (CLL) to the purine analog 2-chloro-2'-deoxyadenosine (CdA) and to assess factors that predict response. PATIENTS AND METHODS We treated 18 CLL patients with about-monthly courses of five daily 2-hour intravenous infusions of 0.12 mg CdA/kg. RESULTS Complete remissions (CRs) were achieved in seven patients (39%), with a total response rate of 67%. CR patients received a median of 4.5 courses. One patient with CR relapsed and died 14 months from start of CdA treatment, whereas the other six patients with CR remain in remission following a mean observation period of 14 months. The median duration of partial remissions (PRs) was 9 months, with a median treatment-free interval of 15 months. Thrombocytopenia was the most common dose-limiting toxicity. Non-responding patients had a median survival of 3.5 months, and systemic fungal infections were the most common cause of death. Immunoglobulin (Ig) levels improved significantly in hypogammaglobulinemic patients during CdA treatment. Responses were predicted by a rapid decrease of blood lymphocyte counts following the first treatment course. CONCLUSION A high CR rate was achieved with limited toxicity. A treatment strategy to enable high-quality response and limitation of treatment-related toxicity is provided.