PB1810 CLINICAL CHARACTERISTICS AND OUTCOMES OF DIFFUSE LARGE B‐CELL LYMPHOMA (DLBCL) LACKING THE IMMUNOGLOBULIN LIGHT CHAIN RESTRICTION (ILCR) BY FLOW CYTOMETRY

Abstract

Background:The immunoglobulin light chain restriction (iLCR) detected by flow cytometric analysis is useful to prove the monoclonality of B‐cell lymphoma. However, we occasionally encounter cases of B‐cell lymphoma without iLCR. The lack of immunoglobulin expression on B‐cell lymphomas arises from abnormalities of gene transcription or translocation of fully assembled proteins on the cell surface. Few reports have evaluated patients of diffuse large B‐cell lymphoma (DLBCL) without iLCR, but the clinical characteristics and outcomes of DLBCL lacking iLCR has not been firmly elucidated.Aims:In the present study, we evaluated the clinical features and prognosis of DLBCL without iLCR.Methods:We conducted a retrospective analysis using a database of our hospital. From April 1, 2007 to March 31, 2017, patients who were performed flow cytometric analysis and diagnosed with DLBCL were eligible. The definition of iLCR was determined when κ‐positive cells were more than 3 times that of λ‐positive cells (κ‐DLBCL) or λ‐positive cells were more than 2 times that of κ‐positive cells (λ‐DLBCL) in dual‐color diagrams. We excluded cases with HIV infection, central nervous system involvement, intravascular lymphoma, primary mediastinal large B‐cell lymphoma, transformation of indolent lymphoma and cases in which flow cytometric analysis did not reflect the lymphoma cells. The endpoints of this study were overall survival (OS) and progression free survival (PFS) of iLCR‐positive/negative DLBCL and κ/λ‐DLBCL. The OS was defined as the time from diagnosis to the last follow‐up or death from any cause. The PFS was defined as the time from diagnosis to disease progression, relapse or death due to any cause.Results:70 patients were identified; 14 cases with iLCR‐negative (20%) and 56 cases with iLCR‐positive (80%), with a median age of 73 years (range 40–86), 80% > 60 years, 44% male, 74% Stage III/IV, 63% IPI high–int/high, 41% were treated with CHOP‐based, 44% THP‐COP‐based (THP‐COP: pirarubicin, cyclophosphamide and vincristine on day 1 and predonisolone on days 1–5) regimen and 91% were combined with rituximab. Median observation time was 605 days (range 2–3223). There were no differences in clinical characteristics with regard to sex, age, serum lactate dehydrogenase (LDH), performance status (PS), stage, number of extranodal lesions, International Prognositic Index (IPI), B‐symptoms and bulky lesion between the two groups. Cell surface markers also showed no difference between iLCR‐positive and iLCR‐negative DLBCL; CD5 (21.4% vs 14.2%; p = 0.72), CD10 (44.6% vs 21.4%; p = 0.138), CD19 (92.8% vs 96.4%; p = 0.494), CD20 (100% vs 91.0%; p = 0.575), CD23 (21.4% vs 10.7%; p = 0.37), CD25 (28.5% vs 41.0%; p = 0.542), CD30 (14.2% vs 1.7%; p = 0.0997), sIgG(35.7% vs 30.4%; p = 0.758), sIgM (50.0% vs 67.9%; p = 0.229). 2‐year‐OS and PFS of iLCR‐positive and iLCR‐negative DLBCL were 61.2% vs 53.9% (p = 0.557) (Fig1) and 51.9% vs 55.0% (p = 0.924) respectively. There are 34 κ‐DLBCL and 22 λ‐DLBCL in 56 iLCR‐positive group. 2‐year OS and PFS of κ‐DLBCL and λ‐DLBCL were 64.3% vs 59.0% (p = 0.746) and 58.6% vs 47.8% (p = 0.255) respectively.Summary/Conclusion:In this study, we observed no difference in the clinical characteristics and outcomes between iLCR‐negative DLBCL and iLCR‐positive DLBCL. In iLCR‐positive DLBCL, the outcome of κ‐DLBCL is similar to that of λ‐DLBCL. Therefore, the presence or absence of iLCR and deviation of κ or λ light chain of DLBCL may not influence on the prognosis and selection of treatment.