EXPRESSION OF MYELOID ANTIGENS BY BLAST CELLS IN ACUTE LYMPHOBLASTIC-LEUKEMIA OF ADULTS - THE SOUTHWEST-ONCOLOGY-GROUP EXPERIENCE

A subset of adult acute lymphoblastic leukemia (ALL) patients have bla st cells which ce-express myeloid-associated antigens (MY+ ALL). We ha ve analyzed 113 adult ALL cases for expression of MY-associated antige ns (MAA). ALL was diagnosed by standard morphology, cytochemistry, and immunophenotype in central review. MY+ ALL was diagnosed when greater than or equal to 20% of lymphoblasts co-expressed CD13 and/or CD33. O verall incidence of MY+ was 31/113 (27%). MAA expression was not signi ficantly correlated with WBC, blast count, hemoglobin, or hematocrit. MY+ cases were more likely to express B-associated antigens, especiall y CALLA, and to be FAB L2, Ph+, or to have the BCR-ABL translocation b y PCR, but these differences were not statistically significant. All p atients were induced with a L10M regimen, and 67 (59%) achieved CR: 43 /66 (65%) of B MY neg; 14/29 (48%) of B MY+; 10/16 (63%) T MY neg; and 0/2 T MY+. In age-adjusted analyses CR rate did not differ significan tly between MY+ and MY neg patients or between B- and T-cell patients. Of the 113 patients, 84 have died and the remaining 29 patients have been followed for a median of 49 months. In proportional hazards regre ssion analyses adjusting for age and WBC, heterogeneity of survival am ong the four groups was statistically significant (p = 0.021), largely due to MY status. The mortality rate was 85% greater for MY+ patients compared to MY neg patients (two-tailed p = 0.013). By contrast, surv ival did not vary significantly between B- and T cell patients. The da ta indicate that MAA expression is useful for predicting overall survi val of adult patients with ALL treated in a L10M protocol. As a predic tive factor MAA expression is comparable to the WBC and superior to th e more standard stratification by B- or T-cell markers for this group of patients.