Thymic Immunophenotype, and Expression of CD4 and Myeloid Antigens is Associated with Outcome in Adult Patients with T�Cell Acute Lymphoblastic Leukemia

Abstract

Background:In adult patients with T-cell acute lymphoblastic leukemia (T-aALL), age, WBC count and cytogenetics are used for prognostic stratification. We report the prognostic significance of immunophenotype in T-aALL patients. Methods:We analyzed 27 T-aALL patients treated at the Leukemia-BMT Program of British Columbia between 1989 and 2010 using a standardized protocol for diagnosis, treatment and follow up. The immunophenotyping raw data was re-analyzed to record positivity (≥20% blasts positive), number of blasts positive, and intensity and homogeneity of expression. Thymic phenotype (TP) and expression of myeloid antigens (My+) were defined as any one of CD1a+ or dual expression of CD4 and CD8, and any one of CD13+, CD33+ or CD117+ respectively.Results: Twenty-two (81%) T-aALL patients achieved complete remission (CR); of these, 7(32%) relapsed within 5-22 months (median 15 months). The relapse-free survival (RFS) and overall survival (OS) were 1 -119 (median 18) months and 1-119 (median 25) months respectively. Frequency of CD1a+, CD4+, TP+ and My+ was 58%, 58%, 66% and 50% respectively. Expression of T-cell antigens CD1a, CD4, and TP+ status were favorably associated with outcome: CD1a+ status with OS (p=0.017), CD4+ status with RFS (p=0.015) and OS (p=0.005), TP+ status with CR (p=0.028) and OS (p=0.024). My+ status was adversely associated with CR (p=0.013) and OS (p=0.026). Conclusions:In T-aALL patients, CD1a+, CD4+ and TP+ are favorably, and My+ status are adversely associated with outcome. The percentage of positive blasts and intensity and uniformity of staining for different antigens shows wide variations.