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In a series of 185 patients (median age 7 years) of acute lymphoblastic leukaemia (ALL) from India, the overall incidence of ALL-1 gene rearrangement using the Southern blot technique was 11.4% (21/185). The incidence amongst the infants (ageor = 1 year, 70%) was significantly higher when compared to patients1 -or = 10 years (7.4%, P = 0.00001) as well as10 years old (9.3%, P = 0.0001). ALL-1 gene rearrangement was associated with significantly higher WBC count (P = 0.01) and CD10 negativity (P = 0.00000001). Complete remission (CR) and relapse rates in 98 patients evaluable for response to therapy on a uniform therapy protocol was independent of ALL-1 gene status.

In 120 cases of acute lymphoblastic leukemia (median age 8 years), IgH chain gene was rearranged in 99% B-Cell Precursor (BCP) ALLs and 13% T-ALLs. One or the other TCR locus was rearranged not only in all T-ALLs, but also in 87% of BCP-ALLs. TCR-beta rearrangement in BCP-ALL was associated with a higher mean age at presentation (8.7 vs. 6.2 years, P=0.008), lower mean platelet counts (61.2x10(9)/l vs. 103.7x10(9)/l, P=0.003) and a poorer DFS (% cummulative survival 0 vs. 88.9+/-10.5, P=0.004). TCR-gamma rearrangement in T-ALL was associated with a higher mean WBC count (186.3x10(9)/l vs. 63. 4x10(9)/l, P=0.002). Also, the pattern of rearrangement of these genes appeared to be different from the West; viz. TCR-beta rearrangement in a higher proportion of BCP-ALLs (58%, 95% confidence intervals 45-69%), invariable deletion of Cgamma1 and only monoallelic rearrangement for TCR-delta locus. This repertoire of gene rearrangement may have a bearing on the poor treatment outcome reported previously from our geographic region.

Thirty-three patients with acute lymphoblastic leukemia (ALL) from India were studied for the presence of BCR-ABL chimeric transcripts, by a seminested cDNA-PCR. We report the presence of BCR-ABL chimeric transcripts in 4/17 (24%) children (under 15 years) and 3/16 (19%) adults (15-50 years). This is in sharp contrast to the published literature from the West where the presence of BCR-ABL has been reported in only 2-5% children and 35% adults. Whether the presence of BCR-ABL fusion mRNA, which is generally an attribute of ALL in adults and of poorer prognosis, may contribute to chemo-incurability in young Indian patients, remains to be seen, as a larger number of patients are studied for treatment outcome and survival on uniform therapy protocols.

Pretreatment immunologic marker analysis in 152 adult and childhood patients of ALL and ALL/lymphoma employing multiple monoclonal antibodies and hetero-antisera revealed three major subgroups, i.e. T-ALL (37.7%), N-ALL (33.1%) and C-ALL (21.5%). The early age peak was absent, males predominated in all the subgroups and T-ALL had increased incidence of thymic mass. Leucocyte counts of 50,000 × 10 6 /1 were equally frequent in the three groups. T-ALL showed marked heterogeneity by showing a variety of markers such as T-helper/inducer, T-suppressor/ cytotoxic, p-24, Ia and CALLA. These results show a high prevalence of unfavourable prognostic factors in ALL in our geographic region which might be related to socioeconomic and/or environmental factors.