Incidence patterns and survival outcomes in primary small intestine B-cell lymphoma (PSIBCL) and the effect of Rituximab.

Abstract

e20025 Background: PSIBCL is a rare manifestation of primary extra-nodal B-cell Non-Hodgkin’s lymphoma and is underreported in literature. We assessed the incidence patterns, and clinicopathologic features and their impact on survival in this population. Methods: Using the SEER database, we identified patients with PSIBCL who were ≥ 18 years old from 1975-2016. Patients were identified using ICD-O-3 and histology codes. Age-adjusted incidence rates were calculated using SEER*Stat 8.36. Using SPSS 26, overall survival (OS) was analyzed using the Kaplan-Meier method and multivariate Cox proportional hazards model was used to determine the prognostic factors. Results: We identified 4810 patients with PSIBCL. PSIBCL accounts for 0.8% of all B-cell Non-Hodgkin’s lymphoma. Age adjusted incidence rose from 0.2 to 0.4 per 100,000 during the study period. Annual percentage change of age adjusted incidence was +2.0 (95% CI 1.4-2.6). Incidence was highest among males, age > 80 years, white & Asian race. The median age of diagnosis was 63 yrs (51-75). 83% presented with either Diffuse large B-cell lymphoma (54%) or Follicular lymphoma (29%). The site of disease was specified in 65%; of those, duodenum (24%), jejunum (15%) and ileum (23%). Staging was reported in 88%; early stage disease (stage I/II) was found in 67%. Median OS for the entire cohort was 27 years (95% CI 23-32) and 5-year OS was 72.6%. Although the incidence was lower in black patients, the 10 year OS was worse (61% black vs 67.4% white). Survival was improved after 1997 (10-year OS rate 71.3% vs 52.0%). These results may correlate to Rituximab approval in 1997. In the multivariate analysis, age > 65, male sex, black race, late stage (stage III/IV), DLBCL and Burkitt lymphoma subtypes were associated with unfavorable OS. Conclusions: Analysis of four decades of data show an upward trend in incidence. PSIBCL has a favorable outcome with a clear survival advantage in patients diagnosed after 1997; this is likely attributable to Rituximab approval.