A Multi-Center, Open-Label Study To Evaluate the Safety and Efficacy of Pentostatin, Cytoxan, and Rituxan (PCR) in the Treatment of Previously Untreated or Treated, Stage III or IV, Low-Grade B-Cell Non-Hodgkin’s Lymphoma (NHL) or Bulky Stage II Lymphoma.

The decision to treat indolent B-cell NHL is often based on progression of the disease. Most regimens have utilized fludarabine as the purine analog but the myelosuppression and immunosuppression of fludarabine combinations frequently results in severe infections. Combination therapy with pentostatin (P), a purine analog, cyclophosphamide (C), a DNA alkylator, and rituximab (R), an anti-CD20 monoclonal antibody, based on the single-agent activities, documented synergy, and non-overlapping toxicity profiles, may represent a promising approach in the treatment of these patients. To further investigate the efficacy of the PCR regimen for the treatment of indolent NHL, we conducted a phase II study. Patients diagnosed of bulky stage II, stage III/IV low-grade NHL (REAL classification), previously untreated or treated, were eligible. All patients were treated with intravenous infusions of P (4 mg/m²), C (600 mg/m²), and R (375 mg/m²) on day 1 of a 21-day cycle for at least 8 cycles. 2 additional cycles were given for patients with PR or SD after cycle 8 or patients with CR/CRu first evident at cycle 8. Clinical evaluation was performed after cycles 2, 4, 6, 8, and 10 if necessary. Dose modification for hematologic toxicity may be increased to the previous higher level when a hematologic toxicity returned to normal. Two 25% dose reductions or one 50% dose reduction were allowed for nonhematologic toxicity. One hundred patients with indolent NHL, 68 previously untreated, 26 previously treated, and 6 with unknown treatment history, were enrolled in the study. The median age was 61 years (range 29–84) and 63.4% were ECOG PS 0, 36.6% PS1. A total of 550 cycles were given, with a median of 6 cycles per patient. 8 patients were not evaluated for response due to withdrawal of consent (n=1), unacceptable toxicities (n=3), and missing data (n=4). 92 patients received at least two cycles of treatment and were evaluated for response. The highest response rate (RR) achieved was 68%, with 10 (10%) CR, 12 (12%) CRu, 46 (46%) PR, 23 (23%) SD, and 1 (1%) disease progression. Stratified according to previous treatment status, patients with previously untreated NHL had an RR of 47% (CR, CRu 17%) while that of the previously treated was 17% (CR 7%). 14 (14.0%) patients discontinued treatment due to toxicities. Grade 3/ 4 hematological adverse events documented included 10 grade 4 and 16 grade 3 neutropenia. Infectious complications were noted in 8 patients including 3 grade 3 febrile neutropenia, 2 grade 4 febrile neutropenia, and 3 grade 3 infections. A total of 4 deaths were recorded, including 1 due to acute myocardial infarction, 1 suspected cardiac event and 2 unknown causes. This immunochemotherapeutic regimen is active in patients with indolent NHL. The study is currently on-going and updated results will be presented.