Pretreatment characteristics and clinical outcome of acute promyelocytic leukaemia patients according to the PML-RAR alpha isoforms: a study of the PETHEMA group.

Of 167 newly diagnosed acute promyelocytic leukaemia patients, 83 patients were long (L)-form (50%), eight variable (V)-form (5%) and 76 short (S)-form (45%). The V-form and S-form groups presented a significantly higher percentage of patients with white blood cell counts > 10 x 10(9)/l (P < 0.05). The S-form cases displayed a significantly higher number of cases with M3v microgranular features (P = 0.005) and CD34 expression (P < 0.0001). There were no differences between the three isoforms in complete remission (CR) rate (overall CR 90%), but the 3-year disease-free survival was lower for V-form cases than it was for L- and S-form cases (62% vs. 94% and 89%, P = 0.056). We conclude that the V-form and S-form types are associated with some negative prognostic features at diagnosis. However, our data were only able to demonstrate an association with adverse prognosis in the V-form type and, moreover, as the number of cases was limited, needs to be confirmed in large, uniformly treated series.