Effect of CD20 Expression Levels On B-Cell Lymphoma Patients' Background and Prognosis.

The anti-CD20 antibody Rituximab has improved the disease-free survival and overall survival of patients with several types of B-cell lymphoma, in which CD20 is expressed on the cell surface and in the cytoplasm. Flow cytometry indicated that CD20 expression varies from null, weak to strong. Despite its clinical importance, the influence of CD20 expression levels on lymphoma therapy has not been well elucidated. Patients, Material and

214 cases were analyzed, all newly diagnosed with B-cell lymphoma at our institute from January in 2002 to April in 2009. All were biopsied and analyzed by flow cytometry. The biopsy specimens were fixed in formalin and stained with Hematoxylin-Eosin; they were also immunostained. Histological subtypes were defined according to the World Health Organization Classification Ver. 3. The mean florescence intensities of CD20 and CD19 were determined by flow cytometry, and cytoplasmic expression of CD20 was determined by immunohistochemistry. 1) The cases were categorized as follows: A: CD20-negative, B: CD20/19 less than 20%, C: CD20/19 20-50% and D: CD20/19 more than 50%. Patients' backgrounds, pathological diagnoses, primary lesions, etc. were also analyzed. 2) Among DLBCL cases, 76 treated with R-chemo were selected and analyzed with respect to treatment response and overall survival.

1) Diagnoses: DLBCL 128, Follicular lymphoma 58, MALT 7, CLL 4 and so on. Among the DLBCL cases, immunohistochemistry indicated six (4%) were CD20-negative and three were CD20-positive; the ages in the CD20-negative DLBCL group tended to be high (74.28 vs 64.36, p=0.06, t-test). Weak CD20 expression was observed in 15 cases (B: 4, C:11). No statistically significant differences were seen with respect to gender, IPI, clinical stage, biopsy lesion, CD5 expression or Karyotype. No FL cases were CD20-negative, but two ( 3.4%) showed low CD20 expression. 2) Kaplan-Meier analysis of 76 cases of DLBCL treated with R-Chemo showed a significantly lower overall survival for Group A, (CD20-negative) while there was no significant difference in overall survival of Groups B+C(CD20-weak) and D(CD20-normal). Our results indicate that even patients with lower levels of CD20 expression in B-cell lymphoma may respond favorably to anti-CD20 therapy. Further studies will be necessary to explore this possibility.

No relevant conflicts of interest to declare.