Site-Specific Survival of Extra Nodal Diffuse Large B-Cell Lymphoma and Comparison With Gastrointestinal Diffuse Large B-Cell Lymphoma.

Background: Diffuse large B-cell lymphoma (DLBCL) constitutes 30% of all non-Hodgkin's lymphomas. It can present as a nodal disease or as an extra nodal disease. Based on the site of origin, extra nodal DLBCL (EN-DLBCL) may have a distinct clinical outcome. Apart from the site of origin, factors including demographics, stage, and presence of any other primary malignancy also affect the outcome. The purpose of our study was to characterize prognostically distinct groups based on the site of presentation of EN-DLBCL. Methods: We used 18 registries in Surveillance, Epidemiology, and End Results database to identify the patients with EN-DLBCL for 2000 - 2015 with last follow-up till December 31, 2018. A total of 30,290 EN-DLBCL patients were selected and categorized based on 13 broad sites grouping. Demographic variables were summarized. We did overall survival analysis with univariate and multivariate Cox-proportional hazard modeling. Short-term survival trend was calculated as well. Results: The percentage of EN-DLBCL of all DLBCLs is 34.48%. EN-DLBCL was comparatively seen more in males (54.94%) and non-Hispanic whites (71.52%). In terms of clinical characteristics, patients with EN-DLBCL were mostly diagnosed at age ≥ 60 years (66.11%), early stage (69.33%), and presentation as first primary cancer (81.89%). A higher risk of mortality was seen in non-Hispanic black (hazard ratio (HR) 1.36), with late age of onset (HR 2.69), late stage at presentation (HR 1.42), and with history of other malignancy (HR 1.29). Compared to the intestinal tract, the risk of overall mortality was higher in individuals with involvement of nervous system (HR 1.85), pancreas and hepatobiliary system (HR 1.22), and respiratory system (HR 1.18) and the best outcomes were seen in heart and mediastinal site (HR 0.58) of DLBCL. Conclusion: Based upon our population-based study, we conclude that primary site of presentation of EN-DLBCL is an important prognostic factor with significant difference in survival based on histological and epidemiological characteristics.