Immunologic and clinicopathologic features of common acute lymphoblastic leukemia antigen‐positive childhood T‐cell leukemia A pediatric oncology group study

The immunologic and clinicopathologic features of common acute lymphoblastic leukemia antigen (CALLA)‐positive and CALLA‐negative T‐acute lymphoblastic leukemia (ALL) and of CALLA‐positive non‐T, non‐B ALL (common ALL) of childhood were compared. Twenty‐seven percent of children with T‐ALL had blasts that expressed CALLA. This expression was not associated with a significantly different incidence of expression of sheep erythrocyte‐rosette receptors, glucocorticoid receptors, peanut agglutinin receptors, or T‐cell antigens. CALLA‐positive T‐cell blasts were more likely to express a p24 leukemia‐associated antigen (CD9, 50% versus 8%) and Ia antigens (39% versus 8%) than were CALLA‐negative blasts. Patients with CALLA‐positive and CALLA‐negative T‐ALL had similar clinicopathologic features at diagnosis. In contrast, compared to patients with common ALL, patients with CALLA‐positive T‐ALL were older, had higher leukocyte counts, and an increased incidence of splenomegaly, lymphadenopathy and mediastinal mass, similar to patients with CALLA‐negative T‐ALL. Patients with CALLA‐positive T‐ALL were more likely to achieve a complete remission (95% versus 83%, P = 0.055) and tended to have an increased duration of event‐free survival (P = 0.07) than did patients with CALLA‐negative T‐ALL. The expression of T‐cell antigens is more important than the expression of CALLA in defining biologically similar subgroups of childhood ALL. Preliminary evidence suggests that within T‐ALL the expression of CALLA may be prognostically important.