e20081 Background: Patients with diffuse large B-cell lymphoma of activated B-cell type (DLBCL-ABC) have a worse prognosis than patients with DLBCL of germinal center origin. Recently, a phase III randomized trial of patients with DLBCL showed no improvement in response rates or progression free survival (PFS) with REPOCH compared to RCHOP. However, the PFS reported in this study was significantly better than expected, indicating that high-risk patients, such as those with DLBCL-ABC, may have been underrepresented. The optimal treatment for patients with DLBCL-ABC remains unknown. Methods: We undertook a retrospective analysis of patients with DLBCL treated in our practice from January 1, 2015 to May 31, 2019. We then examined treatment approaches and outcomes of patients treated for DLBCL-ABC. Results: We treated 136 patients with DLBCL and identified 18 of 136 patients with DLBCL-ABC. There were 9 men and 9 women with a median age of 74 years (range 26-92 years) and a median performance status of Eastern Cooperative Oncology Group 1, (0-2). The median international prognostic index score was 3. Nine of 18 patients were treated with REPOCH, 8 with RCHOP, and one with bendamustine and rituximab (BR). The stage distribution was stage I in 2 patients, stage III in 4 patients, and stage IV in 12 patients. Of 9 patients treated with REPOCH, 9 (100%) achieved a complete remission with no relapses to date. Of 8 patients treated with RCHOP, 6 (75%) achieved a complete remission and 2 had no response and died. The one patient treated with BR failed to respond and died. The median PFS for the 8 patients treated with RCHOP was 19.5 months; whereas, the PFS in the REPOCH group had not been reached at a median follow up of 2 years. Grade 3 and 4 toxicities were more common in the RCHOP group and included cardiomyopathy in 1 patient and two episodes of neutropenic fever (one resulting in septic shock and death). There were no grade 3 or 4 toxicities in the REPOCH group. Conclusions: In this retrospective analysis, our patients with DLBCL-ABC treated with REPOCH had better overall outcomes. A prospective trial in this subset of DLBCL patients is warranted.
S1599 RITUXIMAB MAINTENANCE FOR PATIENTS WITH DIFFUSE LARGE B-CELL LYMPHOMA IN FIRST COMPLETE REMISSION: RESULTS FROM A RANDOMIZED HOVON-NORDIC LYMPHOMA GROUP PHASE III STUDY