Atypical chronic myeloid leukaemia: A case of an orphan disease-A multicenter report by the Polish Adult Leukemia Group.

Atypical chronic myeloid leukaemia (aCML) belongs to myelodysplastic/myeloproliferative neoplasms. Because of its rarity and changing diagnostic criteria throughout subsequent classifications, data on aCML are very scarce. Therefore, we at the Polish Adult Leukemia Group performed a nationwide survey on aCML. Eleven biggest Polish centres participated in the study. Altogether, 45 patients were reported, among whom only 18 patients (40%) fulfilled diagnostic criteria. Among misdiagnosed patients, myelodysplastic/myeloproliferative syndrome unclassifiable and chronic myelomonocytic leukaemia were the most frequent diagnoses. Thirteen patients were male, median age 64.6 years (range 40.4-80.9). The median parameters at diagnosis were as follows: white blood cell count 97 × 109 /L (23.8-342) with immature progenitors amounting at 27.5% (12-72), haemoglobin 8.6 g/dL (3.9-14.9), and platelet count 66 × 109 /L (34-833). Cytoreductive treatment was used in all patients, and 2 patients underwent allogeneic hematopoietic stem cell transplantation. The median overall survival was 14.1 months (95% CI, 7.2), with median acute myeloid leukaemia-free survival of 13.3 months (95% CI, 3.6-22.6). Cumulative incidence of acute myeloid leukaemia transformation after 1 year in aCML group was 12.5% (95% CI, 0%-29.6%). To conclude, aCML harbours a poor prognosis. Treatment options are limited, with allogeneic hematopoietic stem cell transplantation being the only curative method at present, although only a minority of patients are transplant eligible. Educational measures are needed to improve the quality of diagnoses.