Bendamustine Plus Rituximab Is Superior in Respect of Progression Free Survival and CR Rate When Compared to CHOP Plus Rituximab as First-Line Treatment of Patients with Advanced Follicular, Indolent, and Mantle Cell Lymphomas: Final Results of a Randomized Phase III Study of the StiL (Study Group Indolent Lymphomas, Germany).

Abstract 405

Introduction: Promising results have been observed in two phase-II studies evaluating the combination of Bendamustine plus Rituximab (B-R) in patients with relapsed/refractory indolent or mantle cell lymphomas (Rummel et al., JCO 2005; Robinson et al., JCO 2008). In order to further investigate the role of the combination B-R we initiated a multicenter randomized phase-III study in October 2003 to compare efficacy and safety of B-R versus CHOP plus Rituximab (CHOP-R) as first-line therapy for patients with follicular (FL), indolent and mantle cell lymphomas (MCL).

Patients and Methods: 549 patients (pts) in need of treatment for their disease were randomized to receive Rituximab 375 mg/m² (day 1) plus either Bendamustine 90 mg/m² (days 1+2) every 28 days or the standard CHOP regimen every 21 days for a maximum of 6 cycles. The primary endpoint was progression-free survival (PFS). Patients characteristics, including age, stage, LDH, IPI, FLIPI, bone marrow infiltration and extranodal involvement did not statistically significant differ between both arms. The median patient age was 64 years (range 31-83) (64 yrs for B-R and 63 yrs for CHOP-R). Most patients were in stage IV (76,9% in BR and 77,5 in CHOP-R) and stage III (19,2% in B-R and 18,6% in CHOP-R). Histologies were distributed equally between B-R and CHOP-R: follicular 55% and 56%, mantle cell 18% and 19%, and other indolent lymphomas 27% and 24%, respectively. Prophylactic use of antibiotics or growth factors were not generally recommended in this protocol.

Results: Of the 549 pts 36 pts were not evaluable: 10 did not receive any study medication, 9 due to withdrawal of consent, 13 due to incorrect diagnosis (4 × DLBCL, 3 × CLL, 2 × MM, 1 × HD, 3 × solid tumors), and 4 for other reasons. 513 randomized pts are evaluable for the final analysis (B-R: n=260; CHOP-R: n=253). Out of these 9 pts were not evaluable for response evaluation: 4 pts (3 × CHOP-R, 1 × B-R) due to early death in neutropenic sepsis, 3 pts due to a subsequent change of therapy after severe toxicity in 1^st cycle of CHOP-R, 1 B-R pt due to progress of disease, and 1 B-R due to early death. All patients were counted for evaluation of PFS, overall survival (OS), event-free survival (EFS; an event was defined by a response less than a partial response, disease progression, relapse, or death from any cause), and for time to next treatment (TTNT).

A median number of 6 cycles was given in both treatment arms each. 82% of B-R pts and 86% of CHOP-R pts received 6 cycles. At the time of analysis in August 2009, the median observation time was 32 months. Overall response rate for pts treated with B-R was similar to the CHOP-R group (93,8% vs 93,5%, respectively). The CR rate was significantly higher with 40,1% for B-R compared to 30,8% for CHOP-R (p=0.0323). The median PFS, EFS and TTNT were significantly longer after B-R compared to after CHOP-R: PFS 54,8 months for B-R versus (vs) 34,8 months for CHOP-R (p=0.0002), Hazard Ratio (HR) 0.5765 (95% confidence interval (CI) 0.4292 to 0.7683); EFS 54 months for B-R vs 31 months for CHOP-R (p=0.0002, HR 0.6014 (95% CI 0.4515 to 0.7845); and TTNT median not yet reached in the B-R group vs 40,7 months in the CHOP-R group (p=0.0002; HR 0.5416, 95% CI 0.3897 to 0.7491). OS did not differ between both groups at this point of time. Thus far, 67 deaths have been observed (B-R: 34; CHOP-R: 33).

CHOP-R treatment was more frequently associated with serious adverse events (SAE) (n=49 in B-R vs n=74 in CHOP-R). Significant differences in hematologic toxicities were observed for neutropenia grade 3+4 (BR 10,7% vs CHOP-R 46,5%; p<0.0001) and for leukocytopenia grade 3+4 (BR 12,1% vs CHOP-R 38,2%; p<0.0001). G-CSF was more often used in CHOP-R treated pts (20,0% of all cycles) than it was used in the B-R group (4,0%) (p<0.0001). The B-R regimen was better tolerated by the pts as evidenced by a lower rate of alopecia (15% (only grade 1) in B-R vs 62% CHOP-R), a lower number of infectious complications (95 in BR vs 121 in CHOP-R, p=0.0403), a lower incidence of peripheral neuropathy (B-R n=18; CHOP-R n=73; p<0.0001), and fewer episodes of stomatitis (B-R n=16; CHOP-R n=47; p<0.0001). Only drug-associated erythematous skin reaction (urticaria, rash) was more often seen with B-R (n=42) than with CHOP-R (n=23) (p=0.0122).

Conclusions: In this final analysis the combination of Bendamustine plus Rituximab improves PFS and CR rates while showing a better tolerability profile. These promising results suggest that B-R does have the potential to become a new standard first-line treatment option for patients with FL, MCL, and indolent lymphomas.