Prognostic Significance of CD20 Expression in Adult Precursor B-Acute Lymphoblastic Leukemia (B-ALL)
H Jiang, A Jiang, S Samiee, W Xu, J Brandwein, H Chang. University of Toronto, Toronto, Canada
Background: Conflicting results surrounding prognostic significance of CD20 have been reported in pediatric ALL. Recent study indicated CD20 as an adverse prognostic factor in adult B-ALL when treated with hyper-CVAD protocols. To determine the prognostic impact of CD20 expression in adult B-ALL with newer treatment regimens, we studied a large cohort of patients at University Health Network.
Design: We retrospectively analyzed 208 patients with B-ALL diagnosed between 1987 and 2008. Of the 155 patients aged 18-59,115 were treated with a modified pediatric protocol (Dana Farber Protocol, DFP), the other 40 patients received a wide range of treatments, including hyper-CVAD and Protocol C. The 53 patients aged >60 were considered a separate treatment category because their induction regimens were frequently reduced in intensity and duration. The monoclonal anti-CD20 antibody rituximab was not incorporated into any of these protocols.
Results: In our cohort, 93 patients (44.7%) had CD20 expression of at least 20%. CD20 positivity was associated with low platelet counts (p=0.001) but not with other clinical pathologic parameters such as age, gender, WBC count, CNS involvement, t(9;22) status, or other cytogenetic abnormalities. Patients with or without CD20 expression had a comparable 3-year overall survival (OS; 44% vs. 44%, p = 0.99), relapse-free survival (RFS; 50% vs. 42%, p = 0.33) or event free survival (EFS; 40% vs. 34%, p = 0.53). Multivariate analysis found age (>60), high leukocyte count (>30 billion/L), and t(9;22) were associated with an adverse EFS, whereas CD20 expression was associated with a better EFS (p=0.03). Among the 115 patients <60 years of age who were uniformly treated with newer protocols (DFP), multivariate analysis confirmed that t(9;22) and high leukocyte count were associated with shorter EFS, while there was a trend for CD20 expressing patients to have a longer EFS (p = 0.06).
Conclusions: Our data suggests that CD20 expression is not an adverse prognostic factor in adults with B-ALL, and may predict a better outcome when adjusting other risk factors. The discrepancy between our results and the recent report of adverse effect of CD20 expression in B-ALL may be due to the difference in therapeutic regimens. It remains to be determined whether modification of current regimens for adult B-ALL to incorporate CD20-targeted monoclonal therapy would result in a clinical benefit.
Tuesday, March 23, 2010 1:00 PM
Poster Session IV # 185, Tuesday Afternoon