Bendamustine Plus Rituximab Versus Fludarabine Plus Rituximab in Patients with Relapsed Follicular, Indolent, or Mantle Cell Lymphomas – 8-Year Follow-up Results of the Randomized Phase III Study NHL 2-2003 on Behalf of the StiL (Study Group Indolent Lymphomas, Germany)

Introduction: Fludarabine plus rituximab (F-R) is an established treatment option for patients (pts) with relapsed/refractory follicular lymphoma (FL), other indolent lymphoma, or mantle cell lymphoma (MCL). To further improve the treatment in this setting we initiated in 2003 a multicenter, randomized phase III study to compare the efficacy and safety of bendamustine plus rituximab (B-R) versus F-R for pts with relapsed FL, other indolent lymphomas or MCL.

Patients and Methods: 230 pts in need of treatment were randomized to rituximab 375 mg/m² (day 1) plus either bendamustine 90 mg/m² (days 1+2) or fludarabine 25 mg/m² (days 1–3) q 28 days for a maximum of 6 cycles. Prophylactic use of antibiotics or granulocyte-colony stimulating factor (G-CSF) was not generally recommended; however, in case of severe granulocytopenia, G-CSF use was permitted. The primary endpoint was progression-free survival (PFS). Secondary endpoints were overall survival (OS), overall response rate (ORR), and complete response rate (CR). The protocol was amended in 2006 to allow rituximab maintenance therapy (rituximab 375 mg/m² q 3 months for up to 2 years) in both arms, following regulatory approvals in this setting.

Results: A total of 219 pts were evaluable for the analysis (114 B-R; 105 F-R). There were no significant differences between arms for patient characteristics, including age, stage, LDH, IPI, FLIPI, bone marrow infiltration, and extranodal involvement. Most pts had stage IV (71.6% B-R; 60.6% F-R) or stage III disease (21.1% B-R; 25.3% F-R). Median patient age was 68 yrs (range 38–87). Patients had received a median of 1 prior therapy (range 1–7). Histological subtypes were distributed equally between the B-R and F-R arms: follicular, 45.9% and 47.5%, respectively; Waldenström’s Macroglobulinemia, 11.9% and 11.1%; MCL, 20.2% and 21.2%; other indolent lymphomas, 23% and 20.2%. A median of 6 cycles were given in both treatment arms, with 75.2% and 53.4% of B-R and F-R pts receiving 6 cycles, respectively. At the time of this analysis (June 2014), the median observation time was 96 months. The ORR was significantly higher with B-R than with F-R (83.5% vs. 52.5%, respectively; p< 0.0001). The CR rate with B-R was also significantly higher than that with F-R (38.5% vs. 16.2%; p=0.0004). Median PFS was significantly prolonged with B-R compared with F-R (34 vs. 12 months; hazard ratio [HR] 0.54, 95% confidence interval [CI] 0.38–0.72; p<0.0001). The longer PFS translated into a survival benefit with a significantly longer median overall survival in the B-R group than in the F-R group (110 vs. 49 months; HR 0.64, 95% CI 0.45–0.91; p=0.0125) comprising 55 and 71 deaths in the B-R and F-R groups, respectively.

There were no significant differences in the rates of alopecia, stomatitis, erythema, allergic reactions, peripheral neuropathy, or infectious episodes between groups. Hematologic toxicities were also similar between arms: 8.9% grade 3/4 neutropenia with B-R vs. 9.1% with F-R; 11.8% grade 3/4 leukocytopenia with B-R vs. 12.4% with F-R. The overall incidence of serious adverse events was similar for the B-R and F-R groups (17.4% and 22.2%, respectively). 17 pts (14.9%) developed a secondary neoplasia after B-R compared with 16 pts (15.2%) after F-R. Of these, 5 pts in the B-R group, and 3 pts in the F-R group developed a secondary hematological neoplasia (2 AML [1 AML M4], 1 CML, 1 DLBCL, and 1 HD after B-R; and 2 AML M4, and 1 MDS after F-R).

An unplanned subanalysis showed that rituximab maintenance therapy significantly prolonged overall survival (HR 0.38, 95% CI 0.32-0.71; p=0.0003) and PFS (HR 0.35, 95% CI 0.31-0.62; p< 0.0001) in the small group of 40 pts who received this treatment (23 B-R, 17 F-R) compared with those who did not. Although the numbers are too small in this non-randomized comparison to draw validated conclusions, these results appear to confirm the favorable role of rituximab maintenance.

Conclusions: B-R was more effective than F-R in this setting of relapsed FL, other indolent lymphomas and MCL due to higher overall and complete response rates, a longer PFS, and an improved OS. These data confirm the high anti-lymphoma activity of B-R.