Tuesday 6 April 2010

Proportion of Translocations in Childhood ALL in Pakistan is similar to that in India

TEL gene rearrangement due to the 12;21 chromosome translocation is the most common molecular genetic abnormality in childhood acute lymphoblastic leukemia (ALL) and is seen in around 25% of children with pre-B cell ALL (studies mainly from Europe and North America). In this translocation the 5’ part of the TEL (ETV6) gene fuses with almost the entire AML1 (CBFA2) gene, producing the chimeric transcript ETV6-CBFA2.
Figure from www.kreatech,com

It is associated with a better prognosis in ALL . In contrast to the West, the frequency of the translocation TEL/AML1 in children in India with ALL is around 7% (Ref - Siraj et al, Leukemia, June 2003). Now in a study of 50 children with ALL from two institutes in Lahore, Pakistan the frequency of the TEL/AML1 translocation was a similar 6% (Ref - Faiz et al, Journal of Pediatric Hematology Oncology, April 2010). Interestingly, the frequency of another translocation which confers a poor prognosis, t(9;22) or BCR/ABL, was 24% and is much higher than that reported from India and elsewhere.

Clearly, these results are from a hospital-based case series and further larger studies in Pakistan would be necessary. The fact that 42 of these 50 ALL children with ALL were boys illustrates the limitation of such hospital-based case series.

Addendum (08/06/2010) -
A recent report shows that the frequency of TEL/AML1 in Far East Asia (Japan, Korea, China, Hong Kong, Chinese in Singapore, and Taiwan) based on a pooled analysis of 1321 children with ALL was 13.4% (Ref - Liang et al, Pediatr Blood Cancer, 2010). This is lower than that reported from the West but higher than that from the Indian subcontinent.

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