Bcl-6 expression and lactate dehydrogenase level predict prognosis of primary gastric diffuse large B-cell lymphoma

Background/PurposeThe gastrointestinal tract is the most common site of primary extranodal non-Hodgkin lymphoma, and the prognostic factors of primary gastric diffuse large B-cell lymphoma (PG-DLBCL) differ in various studies.MethodsWe retrospectively searched for PG-DLBCL in a single institution, performed immunohistochemical analysis, classified tumor phenotype (Hans and Muris algorithms), reviewed medical records, and analyzed the clinical and immunophenotypic variables using Cox proportional hazard regression model.ResultsA total of 46 cases were identified including 25 males and 21 females with a median age of 63.5; 18 (39%) were at stage I and 28 (61%) at stage II. Seven (15%) patients underwent surgery as initial treatment including total (n = 3, 7%) and subtotal (n = 4, 9%) gastrectomy. Thirty-three patients (72%) received frontline chemotherapy treatment including ten with additional rituximab (MabThera) injection, and two (6%) of these patients developed perforation after chemotherapy. Four patients passed away shortly after diagnosis and the remaining three were lost to follow-up. The overall 2- and 5- year survival rates were 55% and 50%, respectively. The expression of various differentiation markers was CD10 (25%), bcl-2 (50%), bcl-6 (84%), and MUM1 (64%). Half of the cases studied (22/44) were classified as germinal center B-cell (GCB) phenotype and the remaining half as non-GCB according to Hans algorithm; 66% and 34% cases belonged to groups 1 and 2, respectively, according to Muris algorithm. Univariate analysis showed the expression of bcl-6 by the tumor cells as a favorable factor, while elevated serum lactate dehydrogenase (LDH) level, bcl-2 expression, and Muris group 2 were associated with poorer outcome. Multivariate analysis revealed that the two prognostic factors were bcl-6 expression and elevated LDH level, with hazard ratios of 0.09 (p = 0.002) and 3.72 (p = 0.024), respectively.ConclusionIn this retrospective study with heterogeneous treatment modality, we identified bcl-6 expression and elevated LDH level as two prognostic factors for PG-DLBCL.