R-BAC Effective In Patients With Mantle Cell Lymphoma Not Eligible for Intensive Chemotherapy or Autologous Transplant

SAN DIEGO, CA—The rituximab, bendamustine, and cytarabine (R-BAC) chemotherapy regimen was shown to be effective in previously untreated patients >65 years old with mantle cell lymphoma (MCL), as well as in patients who are relapsed or refractory (R/R) to one previous line of immunochemotherapy, based on results of a prospective Phase 2 study presented at the 53rd American Society of Hematology Annual Meeting and Exposition.

In this study, conducted by Carlo Visco, MD of San Bortolo Hospital, Vincenza, Italy, and colleagues, patients received rituximab 375mg/m2 Day 1, bendamustine 70mg/m2 Days 2 and 3, and cytarabine 800mg/m2 Days 2, 3, and 4 of a 28-day cycle for 4–6 cycles.

A total of 37 patients were enrolled in the trial, 20 of whom were previously untreated; 34 were evaluable for response. Median age was 71 years (range 55–88); 60% were males.  Ninety-two percent of patients had Ann Arbor Stage III–IV disease, 44% had bulky disease, and Mantle Cell International Prognostic Index (MIPI) was low/interm/high in 28/18/54% of patients, respectively. Cytologic subtype was blastoid in 17%, and mean ki-67 was 25% (range 5–80).  All R/R patients had rituximab included as part of prior first-line regimens received, six of whom (35%) were refractory to induction therapy. Primary objectives included safety of R-BAC, as well as overall response rate (ORR) and complete response rate (CRR).

The dose-limiting toxicities observed were hematological; 60% of patients experienced transient Grade 3-4 neutropenia, while 90% of patients experienced transient neutropenia and/or thrombocytopenia (median duration two days, range 1–5). Grade 2 anemia was reported in 60% of patients who were transiently treated with erythropoietin. Hematologic toxicities were significantly more common in the R/R patient population than in the treatment-naïve population.

ORR was 88%, while CRR was 74%. For previously untreated patients, CRR was 82% compared with 67% for R/R patients; following the recently revised PET-including response criteria (Cheson BD et al, Journal of Clinical Oncology 2007), CRR was 88% and 73%, respectively. At a median follow-up 13 months from the start of therapy (range 1–28), the  1-year progression-free survival  rate was 76±8%:, 87±8% for previously untreated patients and 62±13% for R/R patients.

Dr. Visco concluded that this study presents evidence that R-BAC is well tolerated and has therapeutic potential when used in an older adult population affected by MCL.