Allogeneic Hematopoietic Stem Cell Transplantation Overcomes the Adverse Prognostic Impact of CD20 Expression In Both Adult and Pediatric Acute Lymphoblastic Leukemia.

We analyzed CD20 expression on pre-B ALL marrow blasts at diagnosis in 157 consecutive patients who underwent allogeneic HCT in first or second complete remission (CR) from 1999–2010. Thirty-two patients with no available flow cytometry data were excluded. Out of 125 evaluable patients, 52 (42%) were < 20 years of age; 73 (58%) were ≥20. All patients had high risk ALL and were in CR at HCT (57% in CR1, 43% in CR2). A majority of patients were Ph+ (60%) and received myeloablative conditioning (84%). Grafts were from sibling (36%), unrelated umbilical cord blood (UCB) (59%) and matched adult URD (5%). CD20+, defined as >20% expression on marrow blasts, was observed in 58 (46%) patients. 55% of children and 39% of adults were CD20+ and expression was similar in CR1 & CR2. Gender, donor source (sibling vs UCB), patient CMV serostatus, cytogenetics (Ph+ vs other), and conditioning (myeloablative vs reduced intensity) was similar in CD20+ and CD20- groups. Disease-free survival (DFS) at 3 years was 48% (95% CI 39–57%) for all patients; 42% (95% CI 30–54%) for CD20- patients, and 55% (95% CI 40–67%) for CD20+ patients (p=0.14). CD20+ expression did not significantly impact relapse rate or DFS in adults (Table) while in patients <20 years CD20+ expression was associated with a slightly favorable relapse rate. Similar overall survival (OS) and DFS was seen in both age groups, independent of CD20 expression. Treatment-related mortality was unaffected at 18% (95% CI 9–27%) and 19% (95% CI 9–29%) in CD20+ and CD20- cohorts, respectively (p= 1.00). In adjusted multivariate regression, the CD20+ group had a slightly but not significantly lower risk of relapse (RR 0.54 [0.27-1.09]; p=0.09), yet similar OS (RR 0.66 [0.38-1.14], p=0.13) and DFS (RR 0.67 [0.39-1.14], p=0.14) compared to the CD20- group.

Pre-B ALL with a CD20+ immunophenotype reportedly confers higher risk of disease recurrence and unfavorable OS with conventional chemotherapy. Our data demonstrates that the poor prognosis associated with CD20+ ALL blasts is overcome by allogeneic HCT. In addition, post-HCT survival is promising in both adults and children, independent of CD20 expression. CD20 targeting monoclonal antibodies may further improve these outcomes.

No relevant conflicts of interest to declare.