Comparing the Number of R-Chop-Like Therapy Cycles (6 Vs. 8 Cycles) for Dlbcl Using Propensity Score-Modified Analysis

Background: Rituximab with cyclophosphamide, doxorubicin, vincristine, and prednisolone every 21 days (R-CHOP-21 therapy) has been the standard therapy for diffuse large B-cell lymphoma (DLBCL) over the last decade. However, the optimal number of CHOP cycles has not been confirmed, as there is no evidence regarding the comparison of outcomes according to the number of R-CHOP-21 cycles. Methods: We analyzed patients with de novo DLBCL in clinical stage II or more; they were diagnosed between November 2002 and December 2012 at our institutions and were treated with 6 or 8 R-CHOP or R-CHOP-like cycles as a first-line regimen for a historical cohort study. Progression free survival (PFS) between 6 and 8 R-CHOP cycles was compared. To avoid patients treated with additional cycles of the therapy for treatment failure, those with ≤6-month PFS were excluded. To adjust for selection bias of patient characteristics between the 6 and 8 cycle groups, propensity scores were calculated using variables including IPI risk factors and laboratory data at diagnosis. Results: In total, 233 patients (male 128, female 105) were enrolled. Median age at diagnosis was 68.7 years (22–93 years). Of these, 150 and 83 patients received 6 and 8 cycles, respectively. Clinical stages were II (n = 91), III (n = 58), and IV (n = 84); revised IPI were very good risk (n = 14), good risk (n = 88), and poor risk (n = 131). No significant differences were detected in PFS between patients treated with 6 cycles and those treated with 8 cycles according to Cox regression analysis using inverse-probability-of-treatment weighting method, based on the propensity scores (HR 1.05; 95% CI 0.68–1.64; P = 0.82). Conclusions: Eight R-CHOP or R-CHOP-like cycles were not superior to 6 cycles. Thus, 6 R-CHOP cycles is sufficient for the majority of patients with untreated DLBCL. A criterion for selecting optimal number of R-CHOP cycles is needed for patients belonging to specific risk groups.