Comparison Between CD20-Negative and CD20-Positive Diffuse Large B Cell Lymphoma; Characteristics and Clinical Outcome

CD20 is a non-glycosylated phosphoprotein expressed on the surface of all mature B-cells. CD20 is expressed on all stages of B cell development except the first and last. However, complete lack of CD20 expression occurred in a few cases without previous rituximab (R-) treatment. The immunohistochemostry (IHC) studies which we used were not perfect for confirmation of expression. However, we intended to investigate characteristics and clinical outcome of CD20-negative diffuse large B-cell lymphoma (DLBCL), not detected with usual method, and to compare with CD20-positive.

The records of Non-Hodgkin's Lymphoma patient registry were reviewed in Asan Medical Center. Between September 2003 and February 2009, a total of 407 patients were diagnosed DLBCL and 16 patients (3.9%) out of 407 confirmed CD20-negative DLBCL by IHC. The rest of patients (n=391) were CD20-positive and unconfirmed cases were excluded. Retrospective analysis of complete response (CR), disease-free survival (DFS), and overall survival (OS) was performed.

The median age was 60.5 years old (range 31–81) in CD20-negative patients. Ten patients were males. The Ann Arbor stage was I in 3 patients, II in 3 patients, and III or IV in 10. Six patients were low risk group, 7 patients in intermediate, and 3 in high risk group according to international prognostic index (IPI). Most of patients (62.5%) received cyclophosphamide, doxorubicin, vincristin, and prednisone (CHOP) chemotherapy in CD20-negative and 295 patients (75.4%) with R-CHOP in CD20-positive DLBCL. The Baseline characteristics was not different in both groups except Hans classifier (p=0.02).

With a median follow-up time of 32.3 months (range 0.5–83.4), the CR rate was 73.5%, the 3-year OS was 69.5%, and 3-year DFS 74.2% in all patients. CD20-positive and CD20 negative groups had a CR rate of 73.7%, 68.8% (p=0.146), respectively, a 3-year OS of 70.7%, 40.0% (p=0.003), a 3-year DFS of 75.4%, 44.6% (p< 0.001), respectively. The 3-year OS and DFS also had significant difference with adjusted IPI (p<0.001, respectively).

CD20-negaive DLBLC was not infrequently with usual IHC method (around 4%). The survival outcome was poor compared with CD20-positive DLBLC because of high relapse rate. It was caused without rituximab treatment in CD20-negative. Development of novel target agents like rituximab should be explored to improve outcome and maintain the CR status of CD20-negative DLBCL.

No relevant conflicts of interest to declare.