Myelodysplastic syndromes following therapy with hypomethylating agents (HMAs): development of acute erythroleukemia may not influence assessment of treatment response.

This study followed 28 patients with myelodysplastic syndromes (MDS) who showed a rise of bone marrow (BM) erythroids to ≥ 50% following three cycles (1-60) of hypomethylating agent (HMA) therapy. If BM blasts were calculated as a percentage of non-erythroids, 12 (42.9%) patients met the diagnostic criteria for acute erythroleukemia, erythroid/myeloid (AEL). However, none of the patients showed clonal cytogenetic evolution or new mutations. When compared to 47 de novo AEL patients, these 12 patients were less anemic and thrombocytopenic, had less complex karyotypes (p = 0.044) and showed a longer survival, either calculated from diagnosis (p < 0.001) or from the time of AEL (p = 0.005). These findings illustrate that ≥ 50% erythroids may appear in BM post-HMA therapy, likely a combination of reduction of BM granulocytes (p < 0.001) and promotion of normal or abnormal erythroid proliferation. Enumeration of blasts as a percentage of non-erythroid cells may lead to a diagnosis of AEL and mis-interpretation as disease progression.

Cytogenetic and clinical assessment of six patients with erythroleukemia.

We report the detailed karyotypic analysis and clinical features of six patients with erythroleukemia (EL). Five of six patients studied displayed substantial numeric and structural chromosome abnormalities. The most common alterations in these patients were monosomy for chromosome 7 and 16. All five patients displaying chromosomal abnormalities presented with 100 percent abnormal metaphases in their bone marrow at the time of initial diagnosis. The remaining patient was studied only during remission and had a normal diploid karyotype in all marrow cells analyzed. No patient in this study had either a Ph1 -chromosome (characteristic of CML), or translocations of chromosome #8-#21 (characteristic of AML-M2). Clinically, all but one patient had a brief history; the exception having had polycythemia rubra vera for 18 years prior to the onset of EL. All patients were treated with current Southwest Oncology Group (SWOG) protocols using cytosine arabinoside and anthracycline combinations. Three of five patients entered complete remission. However, remission durations were short (approximately six months) and median survival just over one year. Cytogenetic analysis of three patients in hematologic remission revealed persistence of chromosomal alterations. It is suggested that such remissions be reclassified as partial rather than complete based upon the cytogenetic information.