Clinical characteristics and outcomes of follicular lymphoma patients with extranodal involvement: analysis of a series of 1090 cases in China

BACKGROUND:Follicular lymphoma (FL) is the most common indolent B cell lymphoma in the world. The clinical features of extranodal involvement in FL were never extensively described. METHODS:We enrolled 1090 patients diagnosed as newly diagnosed FL at ten medical institutions in China from 2000 to 2020 and conducted this analysis and retrospectively explored clinical characteristics and outcomes of FL patients with extranodal involvement. RESULTS:400 (36.7%) patients with newly diagnosed FL had no extranodal involvement, 388 (35.6%) patients had one site of extranodal involvement, and 302 (27.7%) had two or more sites of involvement. Patients with >1 extranodal site had significantly worse PFS (p<0.001), as well as OS (p=0.010). The most common site of extranodal involvements was bone marrow (33%), followed by spleen (27.7%) and intestine (6.7%). In patients with extranodal involvement, multivariate Cox analysis found that male patients (p=0.016), poor performance status (p=0.035), increased LDH (p<0.001) and pancreas involvement (p<0.001) was associated with poor PFS, while the latter three factors were also associated with poor OS. Compared to patients with one site of extranodal involvement, patients with >1 site involvement (p=0.012) had 2.04-fold risk to develop POD24. In addition, multivariate Cox analysis found that the usage of rituximab was not associated with better PFS (p=0.787) or OS (p=0.191). CONCLUSIONS:Our cohort is large enough to have statistical significance in FL patients with extranodal involvement. Male sex, increased LDH, poor performance status, >1 extranodal site, as well as pancreas involvement indicated useful prognostic factors in the clinical setting.