Rituximab followed by cladribine in the treatment of heavily pretreated patients with indolent lymphoid malignancies.

The purpose of this study was to determine the efficacy and toxicity of combined therapy consisting of rituximab (RIT), an anti-CD20 monoclonal antibody, and cladribine (2-chlorodeoxyadenosine, 2-CdA) (RC regimen) in patients with refractory or relapsed indolent lymphoproliferative disorders. Twenty six CD20 antigen positive patients, 15 with B-cell chronic lymphocytic leukemia (B-CLL) and 11 with low grade non-Hodgin's lymphoma (LG-NHL) were enrolled to the study. Fourteen patients (53.8%) had refractory disease, the other 12 (46.2%) were recurrent after prior chemotherapy. RC regimen consisted of RIT at a dose of 375 mg/m2 in 6 h infusion on day 1 and 2-CdA at a dose of 0.12 mg/kg, in 2 h infusion, given on days 2-6. The RC courses were repeated at 4 week intervals or longer if severe myelosuppression occurred. Seventy eight cycles of RC with median of 3 cycles per patient were administered (range 1-5 cycles). Four patients (15.4%) (95% CI 1.5-29.3%), 1 with B-CLL and 3 with LG-NHL, achieved a complete response (CR). Fourteen patients (53,8%) (95%CI 34.6-72.9%), including 10 with B-CLL and 4 with LG-NHL, had a partial response (PR). Overall response rate (OR) was 69.2% (95%CI 51.4-86.9%) in the whole group, from 63.6% (95% CI 35.2 92.0%) in LG-NHL to 73.3% (95%CI 50.1-95.7%) in B-CLL patients. Twelve of 18 patients with CR/PR are still in remission, with the median follow up 10 (7-28 months). The median failure-free survival (FFS) of responders was 6.5 months. Hypersensitivity to RIT was the major toxicity of RC regimen, and occurred in 9 patients (34.6%), mostly only during the first infusion of RIT. Severe neutropenia (grade III) was seen in 3 patients (11.5%). Anemia and thrombocytopenia associated with RC treatment were observed in 5 (19.2%) and 2 patients (7.7%), respectively. Four episodes (15.4%) of grade III-IV infections were observed. There was no treatment related mortality. During the follow-up six patients (23.1%) died from the disease progression. In conclusion, the combination of RIT and 2-CdA is an effective and well tolerated treatment, even for heavily pre-treated patients, and the results seem to be better than in patients previously treated in our institution with 2-CdA alone. This regimen can be considered as an alternative treatment of CD-20 positive indolent lymphoproliferative disorders.