Low frequency of FLT3 gene internal tandem duplication and activating loop mutation in therapy-related acute myelocyticleukemia and myelodysplastic syndrome.

FLT3 gene internal tandem duplication (ITD) and activating loop mutations (D835) were determined in 22 cases of therapy-related acute myelocytic leukemia/myelodysplastic syndrome (t-AML/MDS) and 102 cases of de novo AML/MDS. In t-AML/MDS, FLT3 ITD was absent, and D835 was found in only one case of therapy-related acute promyelocytic leukemia (APL). In de novo AML/MDS, however, FLT3 ITD and D835 were significantly more frequent (28 of 102 cases, P=0.024) and were associated with high peripheral blood and marrow blast counts. Our results suggest that different pathogenetic pathways might be involved in t-AML/MDS and de novo AML/MDS.

Successful treatment of thrombotic microangiopathy after haematopoietic stem cell transplantation with rituximab.

Thrombotic microangiopathy (TMA) is a grave complication after haematopoietic stem cell transplantation (HSCT) and effective treatment is undefined. Five patients with postHSCT TMA, which was refractory to at least 1 week of plasma exchange and prednisolone, were treated with rituximab (375 mg/m(2)/week x 4). Remission was achieved in four patients, of whom three remained in remission and one had died of sepsis at a median follow-up of 10 months. ADAMTS13 levels were low in all evaluable patients, and only one patient showed significant anti-ADAMTS13 antibody. The levels of ADAMTS13 and anti-ADAMTS13 antibody did not change significantly with rituximab-induced remission.

Serial studies of methylation of CDKN2B and CDKN2A in relapsed acute promyelocytic leukaemia treated with arsenic trioxide.

Ninety consecutive patients with acute promyelocytic leukaemia were investigated for promoter methylation of CDKN2B (alias p15) and CDKN2A (alias p16) in disease relapse and progression. CDKN2B methylation was significantly more frequent at first relapse (30/36, 83%) than at presentation (48/77, 62%) (P=0.025), while CDKN2A methylation appeared unaffected. Both acquisition and loss of CDKN2B methylation happened at relapse, with acquisition more frequent. No significant increase in CDKN2B and CDKN2A methylation occurred at more advanced relapses. At first or subsequent relapses, owing to highly effective salvage by arsenic trioxide, CDKN2B methylation did not impact on event-free survival or overall survival.

FLT-3 aberrations in acute promyelocytic leukaemia: clinicopathological associations and prognostic impact.

FLT-3 aberrations that occur as an internal tandem duplication (ITD) or a mutation at the activation-loop position 835, D835, are common in acute promyelocytic leukaemia (APL). We investigated the clinicopathological associations and prognostic impact of FLT-3 aberrations in a cohort of APL patients. FLT-3 exons 11 and 12 were amplified by polymerase chain reaction (PCR), and the ITD was recognized as an increase in the size of the PCR product. FLT-3 exon 17 was amplified, and D835 mutation was identified by loss of an EcoRV site, followed by DNA sequencing. Of 82 patients studied, FLT-3 aberrations were detected in 35 cases (43%) at diagnosis (ITD: 16; D835 mutation: 18; ITD + D835 mutation: 1). FLT-3 ITD, but not D835 mutations, was significantly associated with higher presentation white blood cell count (WBC) and microgranular morphology. Early/induction deaths were related to male sex and high presentation WBC. There was a trend for FLT-3 ITD to be associated with non-remission (P = 0.06). For disease-free survival, high WBC was the only significant adverse factor. Male sex, high WBC and FLT-3 ITD were significant adverse factors for overall survival. These findings have important implications on the possible use of FLT-3 inhibitors in the treatment of APL.