Clinical Characteristics and Outcomes of Follicular Lymphoma Patients with Extranodal Involvement: Analysis of a Series of 1090 Cases in China

Follicular lymphoma (FL) is the most common indolent B cell lymphoma in the world. FL could encounter in several extranodal sites，including bone marrow，gastrointestinal tract，Waldeyer ring and so on. Bone marrow involvement had been testified as poor prognosis in advanced FL patients who received R-CHOP/CVP regimens (Massimo Federico, 2009) (Emmanuel Bachy, 2018). However, the clinical features of extranodal involvement in FL never extensively described. Besides, involvement of ≥2 extranodal sites represents poor prognosis in aggressive lymphoma (Project, 1993), but not in FL. Except bone marrow involvement, the prognostic impact of each involvement site on both localized and advanced-stage FL patients has not yet been fully elucidated. Thus, we conducted this analysis and retrospectively explored clinical characteristics and outcomes of FL patients with extranodal involvement in Chinese population.

We enrolled 1090 patients diagnosed as newly diagnosed FL at 10 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. 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=0.000), as well as OS (p=0.010). The most common site of Extranodal Involvements was bone marrow (33%), followed by spleen (27.7%), intestine (6.7%), parotid gland (5.4%) and Waldeyer ring (4.7%). Patients who had spleen involvement as well as bone marrow and pancreas involvement indicated worse PFS and had high risk of POD24. In patients with >1 extranodal site involvement, rituximab usage in both introduction period and maintenance period, could significantly improve 5-year OS 93.2% (p=0.013) compared to patients who didn't receive rituximab or only use during introduction. Meanwhile, rituximab usage in both introduction period and maintenance period had a trend of OS improvement with 5-year OS 94.0% (p=0.087).

In summary, our cohort is large enough to have statistical significance. >1 extranodal site, as well as spleen, bone marrow and pancreas involvement indicated useful prognostic factors in the clinical setting. Rituximab usage, especially in both introduction period and maintenance period, could help improve overall survival among patients with unfavored prognostic factors.

No relevant conflicts of interest to declare.