The refractory DLBCL population contains a wide spectrum of patients who are not all represented in prospective studies. A subset of patients with less favorable features are included in retrospective analyses, but not in prospective trials for reasons such as symptomatic disease that requires expedited treatment and abnormal laboratory values that deem patients ineligible for clinical trials. Therefore, prospective trials conducted in refractory DLBCL patients should be interpreted cautiously in comparison with retrospective data.