Epidemiology and Determinants of Survival for Primary Intestinal Non-Hodgkin Lymphoma: A Population-Based Study

Background: Gastrointestinal tract is the most common site of extranodal non-Hodgkin lymphoma (EN-NHL). Most of the published data have been on gastric NHL with limited studies on primary intestinal non-Hodgkin lymphoma (PI-NHL) considering rare incidence. We performed epidemiological and survival analysis for PI-NHL from the Surveillance, Epidemiology, and End Results (SEER) 18 database. Methods: A total of 9,143 PI-NHL cases of age >= 18 years were identified from the SEER 18 database for the period 2000 - 2015. Totally, 8,568 patients were included for survival analysis. Cause-specific survival (CSS) and overall survival (OS) analysis were done for PI-NHL and PI-diffuse large B-cell lymphoma (PI-DLBCL) using sex, age of onset, treatment, histology, stage, and year of diagnosis. Survival analysis was done by using Cox proportional hazard model and Kaplan-Meier plot with log-rank test. Results: The percentage of PI-NHL of all the intestinal cancers and EN-NHL were 1.35%, and 10.52%, respectively. The age-adjusted incidence was 0.9145/100,000 population for the study population. PI-NHL was more common among patients aged >= 60 years, male and non-Hispanics Whites. Majority of patients were diagnosed at stage 1 and 2 (74%), and DLBCL (44.8%) was the most common histology. Overall median survival was 111 (95% confidence interval (CI): 105 - 117) months. In OS analysis, significant increased risk of mortality was seen with T-cell NHLs vs. DLBCL (hazard ratio (HR): 2.56), patients aged >= 60 vs. < 60 years (HR: 2.87), stage 4 vs. stage 1 (HR: 1.93), male vs. female (HR: 1.17), with best outcome seen in patient treated with combination of chemotherapy and surgery vs. none (HR: 0.45). Similar results were seen in CSS and for PI-DLBCL as well. Significant improvement in outcomes was observed for PI-DLBCL patients receiving chemotherapy with/without surgery. Conclusions: Findings from our large, population-based study reveal PI-NHL is a rare type of intestinal malignancy with significant difference in survival based on histological and epidemiological characteristics.