Are "early" and "late" T-acute lymphoblastic leukemias different diseases? A single center study of 34 patients

Clinical and biological parameters were retrospectively reviewed in 34 cases of T-lineage acute lymphoblastic leukemia (T-ALL), classified as "early" (20 cases) or "late" (14 cases) subgroups, according to the degree of blast cell differentiation, assessed by immunophenotyping. In "early" T-ALL, age, co-expression of "immature" (CD34 and HLA-Dr) or myeloid (My+) antigens, proliferative activity (as evaluated by Ki67 monoclonal antibody), and expression of the "multidrug-resistance" (MDR) phenotype (as determined by C-219 monoclonal antibody) were significantly higher, while WBC count and expression of CD10 were significantly lower, than in "late" T-ALL. Furthermore, although no statistically significant difference was found between the two groups, "late" T-ALL more frequently displayed a greater extramedullary tumor mass ("lymphoma-like" syndrome), L1 FAB morphology and a normal karyotype. A single patient, with "late" T-ALL, also showed positivity for TCR gamma/delta chains, specific monoclonal antibodies. On the whole, 30 patients (88.2%) achieved complete remission: 16 (80%) were "early" and 14 (100%) "late" T-ALL. No statistical difference was found between the two groups with respect to disease free survival (42% vs 54% at six years), whereas median overall survival was significantly shorter in "early" T-ALL (23 months vs median not yet reached at six years for "late" T-ALL, p <0.05). We conclude that "early" and "late" T-ALL show clinical and biological differences, that could perhaps justify differential therapeutic approaches.