Challenges and perspectives of first-line therapy in patients with diffuse B-cell lymphoma: A review

The neoplasm we refer to as diffuse large B-cell lymphoma (DLBCL) consists of many different subtypes that should not be subject to a single standardized treatment. Critical at the diagnostic stage is the identification of rare (5–10%) but extremely aggressive variants – high grade B-cell lymphomas with MYC and BCL2 and/or BCL6 double-hit (DH) or triple-hit (TH) rearrangement, in which intensive chemoimmunotherapy programs should be applied. The main and most frequent variant of the heterogeneous group of B-cell lymphomas discussed in this publication is diffuse large B-cell lymphoma, not otherwise specified (NOS). Two immunohistochemical subtypes of DLBCL NOS are distinguished, GCB and non-GCB. According to cell of origin, the DLBCL NOS is divided into GCB, ABC, and an unclassified (U) subtypes. In addition, DLBCL NOS includes MYC and BCL2 double-expressor lymphoma (DEL), which is not a unique biological entity, occurs in both GCB and non-GCB subtypes of DLBCL, and is associated with a worse prognosis. Over the past two decades, DLBCL NOS, which accounts for more than 80% of all cases, has been the subject of a growing number of molecular studies that have identified prognostic factors that are being actively introduced into real-world clinical practice. Since the turn of the century, the R-CHOP regimen has been considered the most frequent first line therapy approach for DLBCL NOS, achieving long-term remissions in 60–70% of patients. The worst outcomes when using R-CHOP are recorded in groups at high risk of progression according to the International Prognostic Index (IPI – 3–5), as well as in the presence of unfavorable molecular genetic characteristics of the tumor, such as DEL or ABC subtype of DLBCL NOS. These patient populations benefited the most from the inclusion of polatuzumab vedotin in the initial therapy regimen (Pola-R-CHP). This approach reduced the risk of progression and death in patients with high-risk DLBCL by 30%, reducing the need for second-line therapy by 34%, which can be considered a breakthrough in the last 20 years of searching for improving the "gold standard" of first-line therapy and potentially defining a new standard of therapy for primary patients with high-risk DLBCL.