MLL is involved in a t(2;11)(p21;q23) in a patient with acute myeloblastic leukemia

Prognostic Significance of Complex Karyotypes in Acute Myeloid Leukemia

OPINION STATEMENT

Acute myeloid leukemia (AML) patients with a complex karyotype (CK-AML) show at least 3 unrelated clonal cytogenetic abnormalities with notoriously poor outcome. Such cases fall into either AML with myelodysplasia-related changes or therapy-related AML in the current World Health Organization classification of AML. Allogeneic stem cell transplantation is one of the only treatment modalities that can provide a long-term survival benefit and is recommended as a consolidative treatment in patients who are able to achieve complete remission. Unfortunately, transplantation is also associated with a higher relapse rate and more than half of CK-AML patients relapse from disease within the first 2 years. The probability of achieving remission with traditional induction using cytarabine and daunorubicin or idarubicin ("7 + 3") is so small that investigational therapies should be considered up front in these patients. Less intensive therapeutic backbones, typically using one of the hypomethylating agents, azacitidine or decitabine, minimize toxicity and show a trend toward the improved overall survival. CPX 351 (Vyxeos) is a liposomal formulation of cytarabine and daunorubicin and this encapsulation leads to prolonged exposure to the two drugs. This drug is approved for AML patients with MDS-related changes and therapy-related AML, both of which are frequently associated with complex karyotype. Such patients show improved outcome in trials using this combination. Combination therapy that includes venetoclax (BCL2 inhibitor) with hypomethylating agents may also be appropriate for such patients.

Therapy-related myelodysplastic/myeloproliferative neoplasms with del(5q) and t(1;11)(p32;q23) lacking MLL rearrangement

A 69-year-old man was admitted because of macrocytic anemia and peripheral monocytosis: hemoglobin 75 g/L and white blood cells 16.0x10(9) /L with 22% monocytes. Five years prior, he had received CHOP regimen and radiotherapy for diffuse large B-cell lymphoma. Bone marrow was hypercellular with trilineage dysplasia and 2.4% blasts. Chromosome analysis showed 46,XY,t(1;11)(p32;q23),del(5)(q13q35),+8,inv(9)(p11q13),-15,-21,+mar1. These findings indicated a diagnosis of therapy-related myelodysplastic/myeloproliferative neoplasms (t-MDS/MPN). Fluorescence in situ hybridization revealed that the breakpoint at 11q23 was centromeric to the MLL gene. Taken together with the previously reported cases, trilineage dysplasia and del(5q) without MLL rearrangement suggests that alkylating agents may have a crucial role in the pathogenesis of t-MDS/MPN, which is a rare but recognizable entity.

New complex t(2;11;17)(p21;q23;q11), a variant form of t(2;11), associated with del(5)(q23q32) in myelodysplastic syndrome-derived acute myeloblastic leukemia

The t(2;11)(p21;q23) is a rare recurrent aberration observed in myelodysplastic syndrome (MDS) and acute myeloblastic leukemia (AML). It has been suggested that t(2;11) is specifically associated with a deletion of the long arm of chromosome 5 (5q). A 63-year-old man was initially diagnosed as AML with del(5)(q23q32) as a sole abnormality. At relapse, t(2;11;17)(p21;q23;q11) in association with del(5q) appeared in 14 of 20 cells by G-banding. Spectral karyotyping confirmed three derivative chromosomes, der(11)t(2;11), der(17)t(11;17), and der(2)t(2;17). Fluorescence in situ hybridization analysis with a probe for MLL demonstrated that the breakpoint at 11q23 was telomeric to the MLL gene. Nine of 10 reported cases with t(2;11) and del(5q) had MDS including 5q- syndrome and four of them evolved to AML, as observed in the present case. Our results indicated that t(2;11;17) was a secondary genetic change, which appeared during disease progression after del(5q) was observed. Furthermore, considering another reported case, the MLL gene seems to be not involved in the pathogenesis of MDS/AML with t(2;11) and del(5q).

Integration of molecular methods for detection of balanced translocations in the diagnosis and follow-up of patients with leukemia

Molecular methods are emerging as important tools for the diagnosis and stratification of patients with leukemia. Together with rearrangements in immunoglobulin and T-cell receptor genes, balanced translocations are the most important genetic lesions amenable to molecular diagnosis. Moreover, many publications have identified significant differences in the prognosis of acute leukemia patients with such balanced translocations. Because not all balanced translocations can be diagnosed by cytogenetic techniques, reverse-transcriptase polymerase chain reaction (RT-PCR)-based methods are increasingly employed. This method has the added advantage that it can also be used to monitor for minimal residual disease (MRD). A disadvantage is that the multitude of balanced translocations in leukemia would make efforts to detect all lesions at diagnosis by such standard techniques extremely labor-intensive. Furthermore, difficulties in optimizing semiquantitative PCR assays have limited the utility of these methods for MRD. Recent advances in the design of multiplex PCR, which detects a number of genetic aberrations simultaneously, may improve the diagnostic process. Accurate quantitation of the fusion transcript for balanced translocations has become possible by use of fluorogenic probes and real-time PCR. Together, such methodologies may constitute a novel platform for the integration of molecular methods in clinical decision-making.