Impact of concurrent indolent lymphoma on the clinical outcome of newly diagnosed diffuse large B-cell lymphoma

Some patients with diffuse large B-cell lymphoma (DLBCL) present with a concurrent indolent lymphoma at diagnosis. Their outcomes in the rituximab era are not fully defined. Using a prospectively followed cohort of 1324 newly diagnosed DLBCL patients treated with immunochemotherapy, we defined the prevalence, characteristics, and outcome of DLBCL with concurrent indolent lymphoma. Compared with patients with DLBCL alone (n = 1153; 87.1%), patients with concurrent DLBCL and follicular lymphoma (FL) (n = 109; 8.2%) had fewer elevations in lactate dehydrogenase, lower International Prognostic Index (IPI), and predominantly germinal center B-cell-like (GCB) subtype, whereas patients with concurrent DLBCL and other indolent lymphomas (n = 62; 4.7%) had more stage III-IV disease and a trend toward higher IPI and non-GCB subtype. After adjusting for IPI, patients with concurrent DLBCL and FL had similar event-free survival (EFS) (hazard ratio [HR] = 0.95) and a trend of better overall survival (OS) (HR = 0.75) compared with patients with DLBCL alone, but nearly identical EFS (HR = 1.00) and OS (HR = 0.84) compared with patients with GCB DLBCL alone. Patients with concurrent DLBCL and other indolent lymphomas had similar EFS (HR = 1.19) and OS (HR = 1.09) compared with patients with DLBCL alone. In conclusion, DLBCL patients with concurrent FL predominantly had the GCB subtype with outcomes similar to that of GCB DLBCL patients. DLBCL patients with concurrent other indolent lymphoma had similar outcomes compared with patients with DLBCL alone. These patients should not be summarily excluded from DLBCL clinical trials.