ASH 2024 | A study investigating the impact of DLBCL in the tissue biopsy on outcomes for patients with FL3B

Follicular lymphoma 3B is the most rare among the subtypes of follicular lymphoma, accounting for about 5 to 10% of overall diagnoses. Half of the follicular lymphoma 3B also co-expresses diffuse large B-cell lymphoma, but rarely co-express follicular lymphoma 1 to 3A. The most recent advances suggest that follicular lymphoma 3B has a clinical and biological behavior similar to the aggressive diffuse large B-cell lymphoma rather than follicular lymphoma 1,2,3A, therefore it is treated with immunochemotherapy such as R-CHOP in a similar manner to the diffuse large B-cell lymphoma. Nevertheless, the current literature is also conflicting since some studies reported a survival of about 54%, while others report a survival of 70% to 95%, suggesting more indolent behavior. Additionally, controversy is about the presence or absence of diffuse large B-cell lymphoma in the tissue biopsy, if it can make any difference in the clinical behavior. Therefore, we decided to perform a pooled study of two multi-center prognostic cohorts called MER and LEO American study cohorts and to investigate newly diagnosed follicular lymphoma 3B and compare to follicular lymphoma 1 to 2, follicular lymphoma 3A and DLBCL, all of whom were treated with R-CHOP chemotherapy within six months of diagnosis. What we found is that having or not having diffuse large B-cell lymphoma in follicular lymphoma 3B did not make a significant difference in clinical characteristics of patients. Additionally, we then compared the pooled follicular lymphoma 3B with the lower-grade follicular lymphoma and we found that FL1 to FL2 relapsed more frequently and also relapsed more frequently within 24 months of diagnosis compared to follicular lymphoma 3B and 3A. Nevertheless, the follicular lymphoma 3B that did fail event-free survival at 24 had a threefold likelihood to die of disease compared to the other follicular lymphoma and also had a 2-rate more probability to transform toward an aggressive lymphoma. We also compared the follicular lymphoma 3B to diffuse large B-cell lymphoma subcharacterized by cell of origin of germinal center or non-GCB, and we found that FL3B was more similar to GCB rather than non-GCB. We then concluded that follicular lymphoma 3B with or without DLBCL has similar clinical and outcome characteristics. And while the most part of follicular lymphoma 3B behaves as lower-grade FL1 to 3A, 18% has a more aggressive behavior and is more similar to diffuse large B-cell lymphoma.

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