The LNH03-6B trial was a phase 3 randomized trial evaluating the efficacy of first-line rituximab, cyclophosphamide, doxorubicine, vincristine and prednisone (R-CHOP) delivered every 2 weeks (R-CHOP14) or 3 weeks (R-CHOP21) in patients with diffuse large B-cell lymphoma (DLBCL) aged 60 to 80 years with an aaIPI (age-adjusted International Prognostic Index) score ≥1 (registered as NCT00144755). We implemented a prospective long-term follow-up program at the end of this trial. The primary endpoints were progression-free survival (PFS) and overall survival (OS). Relapse patterns, PFS and OS after the first progression (PFS2 and OS2) were secondary endpoints. LNH03-6B was registered with ClinicalTrials.gov #NCT00144755. In the LNH03-6B trial, 304 and 296 patients were assigned to receive 8 cycles of R-CHOP14 or R-CHOP21, respectively. Long-term follow-up data were investigated for 256 of 384 (67%) patients still alive at the primary analysis. With a median follow-up of 10.1 years, 213 patients progressed, and 140 patients died without progression. The 10-year PFS was 40.4% (95% confidence interval, 35.9-44.9). Ten-year OS was based on 302 deaths and estimated at 50% (43-56). Of the 213 patients, 105 (49%) progressed after second-line therapy, and 77 patients died without a second progression (36%). The 1-year PFS2 and 1-year OS2 were estimated at 37.9% (95% confidence interval, 31.4-44.5) and 55.8% (95% confidence interval, 48.8-62.2), respectively. Ten years after randomization, the outcomes of patients treated for DLBCL were similar according to PFS and OS between the RCHOP-14 and R-CHOP21 groups. Progression or relapse led to poor prognosis after second-line chemotherapy in the pre CAR-T-cell era. Novel approaches in first-line and alternative treatments in second-line treatments are warranted in this population.