Autologous Stem Cell Transplantation and Addition of Rituximab Independently Prolong Response Duration in Advanced Stage Mantle Cell Lymphoma.

In younger patients with mantle cell lymphoma (MCL), autologous stem cell transplantation (ASCT) significantly prolonged response duration with a trend towards improved overall survival in a randomized trial of the European MCL Network (Dreyling et al., ASH 2008). A recently updated clinical trial of the German Low-Grade Lymphoma Study Group (GLSG) also reported a significantly prolonged response duration by the addition of Rituximab to first-line CHOP (Hoster et al., ASH 2008). By pooled analysis of these trials we investigated whether Rituximab and ASCT independently prolong response duration.

The analysis included all advanced stage MCL patients of the trials “CHOP vs. MCP” (Nickenig et al., Cancer 2006), “CHOP vs. R-CHOP” (Lenz et al., JCO 2005) and European MCL trial 1 (Dreyling et al., Blood 2005) with complete or partial remission to either CHOP or R-CHOP first-line induction and randomization between ASCT and Interferon-α maintenance. Response duration was defined as time from the end of successful induction chemotherapy to relapse or death from any cause, overall survival from the end of successful induction chemotherapy to death from any cause. Stratified Kaplan-Meier curves for response duration and overall survival were calculated for the four treatment groups (CHOP without ASCT, CHOP with ASCT, R-CHOP without ASCT and R-CHOP with ASCT). By multiple Cox regression we tested whether the impact of Rituximab (R) and ASCT was independent and additive.

One-hundred and eighty patients with MCL were evaluable, 80 treated with R-CHOP, 78 with ASCT (CHOP without ASCT: 56, CHOP with ASCT: 46, R-CHOP without ASCT: 44 and R-CHOP with ASCT: 34). Median age was 55 years (range 34-65), the MIPI classified 71% as low risk, 22% as intermediate risk, and 6% as high risk, and baseline characteristics were comparable between treatment groups. With a median follow-up of 63 months, median response duration was 16 months after CHOP without ASCT, 26 months after R-CHOP without ASCT, 39 months after CHOP with ASCT, and 41 months after R-CHOP with ASCT. In multiple Cox regression including R and ASCT, the hazard ratios of R (0.60, 95% CI 0.42-0.86, p = 0.0056) and ASCT (0.50, 95% CI 0.35-0.70, p = 0.0001) were independently significant. There was no interaction between R and ASCT (p=0.43). Median overall survival was 54 months after CHOP without ASCT, 66 months after R-CHOP without ASCT, 90 months after CHOP with ASCT, and not reached after R-CHOP with ASCT. The hazard ratios for OS were 0.70 (95% CI 0.44-1.12, p = 0.14) for R and 0.63 (95% CI 0.41-0.97, p = 0.0379) for ASCT.

Our results indicate an additive effect of ASCT and Rituximab in combination with CHOP on response duration in advanced stage MCL patients and support strategies of several study groups to combine Rituximab-containing induction therapies with ASCT in younger MCL patients. However, even after combined treatment approaches, delayed relapses have been observed, supporting the use of maintenance therapy and the introduction of molecular targeted therapeutical strategies.

Hoster:Roche: Travel Support. Off Label Use: Rituximab in Mantle Cell Lymphoma. Pfreundschuh:Roche: Membership on an entity's Board of Directors or advisory committees. Dührsen:Roche: Honoraria, Research Funding; Amgen: Honoraria, Research Funding. Gisselbrecht:Roche: Research Funding, Speakers Bureau. Unterhalt:Roche: Travel Support. Dreyling:Roche: Honoraria, Research Funding.