Reverse transcription polymerase chain reaction for the diagnosis and molecular monitoring of the PML/RAR alpha fusion gene in acute promyelocytic leukemia

Intensified myeloablative therapy and autologous stem-cell transplantation for patients with AML: single center experience

BACKGROUND

Thirty-seven consecutive individuals in CR of AML received intensified conditioning and autologous stem-cell transplantation.

METHODS

For those receiving PBSC (n = 28), mobilization protocol was with cyclophosphamide 60 mg/kg followed by G-CSF injection at 5-10 microg/kg; stem cells were harvested by large volume apheresis (6-8 blood volumes) and then cryopreserved. Ablative therapy consisted of fractionated TBI (total 12 Gy), followed by four fractions (1.5 Gy each) of total nodal irradiation (TNI), and CY 120 mg/kg under mesna cover.

RESULTS

For individuals transplanted in CR 1 (n = 31) the median time from diagnosis to grafting was 167 (range 92 - 212) days. Patients transplanted with PBSC received high number of CFU-GM x 10(4)/kg (P < 0.01), a difference that was associated with a significantly shorter platelet recovery. While there was no early transplant-associated mortality, in 10 patients death was caused by recurrence of the disease. The median survival is 1746 (range 105-4467) days and 26 (70%) survive disease free, at a median 2207 (range 698-4467) days from transplantation. Multivariate analysis showed that survival of patients with AML-M3, receiving higher CFU-GM (P = 0.04) and without morphological dysplasia (P = 0.01) was longest.

DISCUSSION

For patients in remission of AML, transplantation with PBPC appears to be an effective form of intensification, particularly when TBI + TNI (delivering a total of 18 Gy to the axial skeleton) were used as conditioning.

Acute promyelocytic leukemia M3: cytomorphologic, immunophenotypic, cytogenetic, and molecular variants

Acute promyelocytic leukemia (APL) M3 is an acute myeloid leukemia (AML) subtype characterized by proliferation of malignant promyelocytes with mature myeloid immunophenotype and the translocation t(15;17)(q22;q11), which results in the fusion of retinoic acid receptor-alpha (RARalpha) gene on chromosome 17 and the gene PML on chromosome 15. There are three M3 morphologic variants: the typical hypergranular form and the microgranular and basophilic variants. Although most leukemic cells in M3 patients express t(15;17), other cytogenetic abnormalities have also been reported. Also, there are three molecular variants of the PML/RARalpha transcript (bcr1, bcr2, bcr3). Blasts had typical hypergranular appearance (13 patients) with a mature myeloid immunophenotype (HLA-DR(-),CD13(+), and/or CD33(+)) (10 patients) in the majority of patients with M3 followed in this study. The typical translocation [t(15;17)(q22;q11)] was detected by cytogenetic analysis in 5 M3 patients, but PML/RARalpha was positive in 13 out of 15 patients, as assessed by RT-PCR (8 patients with bcr1 and 5 with bcr3 subtype). Cytogenetic diversity was found in three patients (1 with t(17;17), 1 with +8, and 1 with add (7)(q22); -7; +8). According to many studies, leukemic cell heterogeneity in APL influences the clinical outcome of disease. The analysis of certain leukemic cell characteristics on the clinical outcome in our study revealed that patients with bcr3 had shorter medians of first remission and survival in comparison to patients with the bcr1 isoform of PML/RARalpha. Also, the clinical relapse of disease in 4 APL patients with reverted PML/RAR alpha positivity is consistent with the view that detection of PML/RARalpha by RT-RCR in patients in remission implies a poor prognosis. On the contrary, lack of detection of PML/RARalpha by RT-PCR at least three times is a sign of long remission and survival.