Prognostic Factors

While the presence of the t(15;17) or PML-RARA fusion confers an overall "good" prognosis to APL patients, there nevertheless exists a subset of APL patients who are at high risk of relapse or death despite best available therapy. In 2000, Spanish (PETHEMA: Programa de

Estudio y Tratamien to de las Hemopatias Malignas) and Italian (GIMEMA: Gruppo Italiano Malattie Emato logiche dell' adulto) APL investigators defined low-, intermediate-, and high-risk subgroups of APL patients based on presenting white blood cell (WBC) and platelet counts (low risk: WBC count <10,000/^L and platelet count >40,000/^L; intermediate risk: WBC count <10,000/^L and platelet count <40,000/^L; high risk: WBC count >10,000/^L).4 Based on the above analysis, as well as on data from numerous other groups, it is now well known and accepted that APL patients who present with WBC counts of more than 10,000/^L have a high risk of treatment failure, due both to an increased incidence of deaths during induction and to a higher risk of relapse. Specific genetic findings, such as the bcr-3 PML breakpoint5 and internal tandem duplication (ITD) of the FLT3 gene,6-9 as well as microgranular morphology, are associated with high WBC count, but have not, in general, been found to have independent prognostic significance in patients treated with modern all-£ra«s-retinoic acid (ATRA)-based regimens. Also, there is no independent prognostic significance of chromosomal abnormalities in addition to the t(15;17) in patients treated with ATRA-containing regimens.1011 Certain immunophenotypic findings seem to be associated with poor prognosis, specifically expression of CD2, CD34, and CD56, but only CD56 expression has been shown to have independent prognostic significance.1213

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