AbstractOutcomes of diffuse large B-cell lymphoma (DLBCL), either concurrent with or transformed from indolent lymphoma, treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone are described in retrospective studies. The efficacy of other regimens in transformed or concurrent DLBCL is largely unknown. In this single-center retrospective study, we present characteristics of concurrent and transformed DLBCL and outcomes after dose-adjusted etoposide, vincristine, cyclophosphamide, prednisone, and doxorubicin with rituximab (DA-EPOCH-R) comparative with de novo DLBCL. Of 170 patients with DLBCL, 136 were de novo, 17 were concurrent, and 17 were transformed. Transformed DLBCL had significantly lower complete response rates and progression-free survival (PFS) but similar overall survival (OS) compared with de novo counterpart. There was no significant difference between de novo and concurrent DLBCL regarding response rates, PFS, and OS. DA-EPOCH-R was associated with inferior OS. Thus, intensified treatment with DA-EPOCH-R might not improve outcomes of transformed DLBCL.