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 a s ''early'' (20 cases) or ''late'' (14 cases) subgroups, according to the degree of blast cell differentiation, assessed by immunophenotypin g. In ''early'' T-ALL, age, coexpression of ''immature'' (CD34 and HLA -Dr) or myeloid (My+) antigens, proliferative activity (as evaluated b y Ki67 monoclonal antibody), and expression of the ''multidrug-resista nce'' (MDR) phenotype (as determined by C-219 monoclonal antibody) wer e significantly higher, while WBC count and expression of CD10 were si gnificantly lower, than in ''late'' T-ALL. Furthermore, although no st atistically 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 kar yotype. A single patient, with ''late'' T-ALL, also showed positivity for TCR gamma/delta chains, specific monoclonal antibodies. On the who le, 30 patients (88.2%) achieved complete remission: 16 (80%) were ''e arly'' and 14 (100%) ''late'' T-ALL. No statistical difference was fou nd between the two groups with respect to disease free survival (42% v s 54% at six years), whereas median overall survival was significantly shorter in ''early'' T-ALL (23 months vs median not yet reached at si x years for ''late'' T-ALL, p < 0.05). We conclude that ''early'' and ''late'' T-ALL show clinical and biological differences, that could pe rhaps justify differential therapeutic approaches.