Prednisone response is the strongest predictor of treatment outcome in infant acute lymphoblastic leukemia.

To define prognostic factors in infant acute lymphoblastic leukemia (ALL), the outcome of 106 infants (age /=1,000 blasts/microL) received intensified therapy. Infant ALL was characterized by a high incidence of a white blood cell count greater than 100 x 10(3)/microL (57%), central nervous system leukemia (24%), lack of CD10 expression (59%), 11q23 rearrangement (49%) including the translocation t(4;11) (29%), and a comparatively high proportion of PPR (26%), which were all significantly associated with inferior outcome by univariate analysis. The estimated probability for an event-free survival at 6 years (pEFS) was by far better for PGR compared with PPR, who had a dismal prognosis despite intensified treatment (pEFS, 53% +/- 6% v 15% +/- 7%, P =.0001). Infant PGR, who were less than 6 months of age (n = 40), lacked CD10 expression (n = 43), and/or had an 11q23 rearrangement (n = 17) fared significantly better compared with corresponding PPR, as indicated by a pEFS of 44% +/- 8%, 49% +/- 8%, and 41% +/- 12%, respectively. In multivariate analysis, PPR was the strongest adverse prognostic factor (relative risk, 3.3; 95% confidence interval, 1.9 to 5.8; P <.0001). Infants with PGR, comprising a major subgroup (74%) among infants, might successfully be treated with conventional therapy, whereas PPR require new therapeutic strategies, including early treatment intensification or bone marrow transplantation in first remission.