Gastrointestinal follicular lymphoma: using primary site as a predictor of survival.

Gastrointestinal follicular lymphoma (GI-FL) is a rare extranodal variant of follicular lymphoma (FL) that has been increasingly reported in the literature. An especially indolent course is linked to the disease after a lack of observed patient death in past studies. However, overall survival (OS) and associated prognostic factors remain unclear. A large population-based database was utilized to identify demographic and clinicopathologic characteristics of GI-FL, along with survival differences among primary sites. The Surveillance, Epidemiology, and End Results Registry was used to identify GI-FL cases between the years of 1973 and 2012. Kaplan-Meier curves compared OS differences and Cox proportional hazard models analyzed prognostic factors. Final analysis included 1109 cases. Small intestinal cases, which included those with single-site and multi-segment involvement, were most common (63.6%) followed by gastric (18.2%) and colorectal cases (18.2%). Small intestinal GI-FL presented more frequently with grade I histology, and less often with grade III histology (P < 0.001 and P < 0.001, respectively). Small intestinal cases had better outcomes (5-year OS = 80.9%, P < 0.001) compared to cases involving the stomach (5-year OS = 52.7%) and colorectum (5-year OS = 71.5%). On multivariate analysis for predictors of mortality, small intestinal involvement predicted for better survival; hazard ratio (HR) 0.66 (95% CI: 0.51-0.85). Advanced age (≥66), grade (grade III), and stage (Ann Arbor Stage III/IV) predicted for mortality with HR 5.46 (95% CI: 3.80-7.84), 1.42 (95% CI: 1.10-1.83), 1.57 (95% CI: 1.15-2.16), respectively. GI-FL has poorer outcomes than previously suggested. Small intestinal involvement has a better prognosis. A possible biological basis for this will require further investigations in the future.