Introduction
Among common types of non-Hodgkin’s lymphoma, diffuse large B-cell lymphoma (DLBCL) accounts for approximately 35% of lymphoma cases in western countries (1-3). Most often, chemoimmunotherapy with standard regimens such as R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine prednisone) is the treatment for DLBCL patients. However, prognosis of these patients is highly heterogeneous and it is very difficult to predict the final outcome of the disease in the patients. In addition, about 40% of DLBCL patients experience relapse or are resistant to treatment (4, 5).
In the recent years, several prognostic factors such as Hemoglobin, Lymphocyte/Monocyte Ratio, Beta-2 microglobulin, and Neutrophil/Lymphocyte Ratio have been proposed to project the survival rate of DLBCL patients (6-9). Nevertheless, easier and more available factors with high sensitivity are required for prediction of prognosis of DLBCL patients. Red blood cell distribution width (RDW) is considered a systemic inflammatory response marker that can be easily evaluated through the Complete Blood Count (CBC) test and has acceptable sensitivity in many diseases such as cardiovascular and autoimmune diseases and sepsis (10-13). D-Dimer as a sensitive index of the process of fibrin formation and destruction is widely used in the deep venous thrombosis detection, intravascular coagulation, sickle cell anemia, and myocardial infarction (14-18). Recent studies introduced that tumor-related degradation products for the coagulation and fibrinolytic system, such as D-Dimer, can be used as outcomes prediction for tumor (19). Furthermore, scientific evidence recently revealed the association of RDW and D-Dimer with many cancers such as breast cancer (20-22), lung cancer (23, 24), blood cancers (25-27), prostate cancer (28), and other malignancies (29-32). However, the prognostic roles of RDW and D-Dimer in cancer and its possible mechanism in tumor progression are being discussed. Besides, several studies indicated that D-Dimer had a possible role in proliferation of cancer cells, adhesion, and angiogenesis, which may bring about malignant tumors growth. Cancer patients usually face hypercoagulable states that increase the risk of embolism. Hence, D-Dimer levels have prognostic role and are associated with survival of patients with cancer. Considering the differences between the results of the studies regarding sample sizes, study designs, and the controversy among the results, we deemed it necessary to conduct a meta-analysis regarding comprehensively investigating the RDW and D-Dimer prognostic roles among patients with DLBCL.