Prognostic relevance of the expression of Tdt and CD7 in 335 cases of acute myeloid leukemia

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Abstract
We have analyzed the expression of Tdt and CD7 in 335 cases of unequivocal acute myeloid leukemia (AML). Tdt was expressed in 80 (25%) of 321 evaluable cases. Twenty-six of 77 (34%) Tdt+ patients assessable for response, entered complete remission (CR) vs 121 of 209 (58%) Tdt− cases (P < 0.001). cd7 was expressed in 102 of 332 (30%) evaluable cases; 37 of 93 assessable (40%) cd7+ patients attained a CR as compared to 114/204 (56%) CD7− (P = 0.013). Duration of survival was significantly shorter for patients with CD7+ or Tdt+ AML (P = 0.006 and 0.001, respectively). In a multivariate analysis, Tdt was found to significantly adverse achievement of CR (P = 0.018), while CD7 affected duration of CR (P = 0.037). Overall the expression of either Tdt or CD7 correlated with a relatively high expression of CD34 (P < 0.001), gp-170 (P = 0.003), lymphoid antigens (LyAg) (P < 0.001), t(9;22) or anomalies of chromosome 5/7 (P < 0.001). finally, we pooled the patients into four phenotypic classes, according to the presence of tdt, cd7 or both: [tdt−CD7−], [Tdt+CD7−], [Tdt−CD7+] and [Tdt+CD7+]. The category [Tdt+CD7+] was characterized by a more unfavorable outcome as suggested by a lower rate of CR (P < 0.001) and a shorter duration of survival as compared to cases [tdt−CD7−], [Tdt+CD7−] and [Tdt−CD7+] (P = 0.002). This figure is consistent with the frequent convergence in the subset [Tdt+CD7+] of GP-170 positivity (P = 0.003), translocation t(9;22), anomalies of chromosome 5 and/or 7 (P < 0.001) and signs of lineage infidelity (deviant expression of lymphoid antigens) (P < 0.001). we conclude that the expression of tdt or cd7 is associated with an unfavorable outcome and that the combination of both defines a clinical subset with a poorer prognosis due to the significantly higher association with mdr phenotype, and ‘poor prognostic’ chromosomal abnormalities.

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