R-CHOP Versus (vs) CHOP Followed by Maintenance Rituximab (MR) Vs Observation In Older Diffuse Large B-Cell Lymphoma (DLBCL) Patients (pts): Long-Term Follow-up of Intergroup E4494/C9793

Abstract

Abstract Abstract 589 Background: The initial results of this intergroup trial with median follow-up of 3.5 years (yrs) were previously reported (J Clin Oncol 24:3121, 2006). We present updated results with median follow-up of 9.4 yrs from induction therapy randomization, and 9.0 yrs from maintenance randomization. Methods: 632 patients (pts), age >60 yrs, with DLBCL were randomized to CHOP+rituximab 375 mg/m2 IV, administered Day -7, -3, and two days before cycles 3/5/7 (if given) (R-CHOP), versus CHOP, for two cycles beyond best response for 6–8 cycles total. Pts were stratified by the International Prognostic Index (IPI) (<3 vs >3). 415 pts responding to R-CHOP or CHOP were then randomized to maintenance rituximab 375 mg/m2 weekly times 4, every 6 months for 2 yrs starting 4 weeks after the last chemotherapy (MR, n=207), or observation (OBS, n=208). Results are presented for the 546 (267 R-CHOP; 279 CHOP) pts for induction, and 352 (174 MR; 178 observation) evaluable, centrally reviewed, maintenance pts. Failure-free survival (FFS) was the primary endpoint. The stratified weighted Cox regression was used to remove the effect of MR in comparing induction treatment, and stratified log-rank test used to assess maintenance effect. Results: Baseline characteristics and response to induction were balanced. 9-yr FFS and OS) are 35% and 44% for R-CHOP, and 25% and 37% for CHOP. Compared with CHOP, R-CHOP significantly prolonged FFS (p=.008), but not OS (p=.11). Pts were categorized into low-risk (LR) and high-risk (HR) groups according to their IPI (<3 or 33) (LR, n=217; HR, n=327). A significant difference in the effect of induction therapy was observed for high-risk patients only for FFS (p=0.02, HR=0.61, 95% CI, 0.51 to 0.93) but not for OS. MR significantly prolonged FFS (log-rank p=0.018, HR=0.71, 95%CI, 0.54 to 0.94), but not OS (p=0.44, HR=0.89, 95%CI, 0.65 to 1.20). A significant interaction between maintenance and induction therapies was observed in that MR significantly prolonged FFS after CHOP (p=0.003, HR=0.56, 95%CI, 0.38 to 0.82), but not after R-CHOP (p=0.89, HR=0.97, 95% CI, 0.64 to 1.47). There was no OS difference with MR after CHOP (p=0.19, HR=0.76, 95% CI. 0.50 to 1.15) or R-CHOP (p=0.77, HR=1.07, 95% CI, 0.68 to 1.68). Median time to failure after maintenance randomization following CHOP+MR was 9.5 yrs vs 2.0 yrs for CHOP+OBS (p=0.003) and following R-CHOP+MR was 8.5 yrs vs 7.5 yrs for R-CHOP+OBS (p=NS). Proportionately more treatment failures occurred within 2 yrs after CHOP+OBS (73%) compared to CHOP+MR (47%), p=0.01. In contrast, the proportion of failures within 2 yrs was similar for R-CHOP+OBS (38%) and R-CHOP+MR (36%), p=NS. Conclusions: Initial R-CHOP therapy, as compared with CHOP, resulted in improved DFS and FFS for older DLBCL pts. MR after CHOP, but not after R-CHOP, significantly prolonged time to failure but did not prolong OS. However, FFS was 42% at 9 yrs among R-CHOP responders, with or without MR. Future treatment strategies should build upon these findings in this older patient population, often with significant co-morbidities. Disclosures: Morrison: merck: Consultancy, Membership on an entity's Board of Directors or advisory committees; celgene: Consultancy, Speakers Bureau; amgen: Consultancy, Speakers Bureau; genentech: Speakers Bureau; pfizer: Speakers Bureau. Fisher:roche: Consultancy. Horning:Genentech: Employment.