Clinical Characteristics and Outcomes of Acute Megakaryoblastic Leukemia With t(1;22)(p13;q13) in Children

The t(1;22)(p13;q13) chromosome abnormality is reported in 10%-17% of children with acute megakaryoblastic leukemia (AMKL), leading to the chimeric fusion gene RBM15::MRTFA. Previous studies have revealed that AMKL with t(1;22) exhibits a good prognosis; however, early death has been observed in cases with onset of the disease at birth and liver failure.

To determine the clinical characteristics and outcomes of AMKL with t(1;22), we conducted a nationwide retrospective survey.

AMKL with t(1;22) was diagnosed in 23 children (eight boys and 15 females) from 2000 to 2013. Their median age at diagnosis was 4 months (range: 0-34 months). Hepatosplenomegaly was observed in 17 patients, with three initially misdiagnosed as solid tumors. G-banding revealed t(1;22) in 21 patients, and PCR detected the RBM15::MRTFA fusion gene in two other patients. The 5-year overall survival (OS)/event-free survival (EFS) rates in all patients were 52%/35%. Eight patients aged less than 6 months at diagnosis and had hepatomegaly (≥6 cm under the right hypochondrium) demonstrated significantly lower 5-year OS/EFS rates (25%/0%) than the remaining 15 patients (67% [p = 0.008]/25% [p < 0.001]). Among 16 patients treated with intensive chemotherapy, the 5-year OS/EFS rates were significantly higher (63%/44%) than those of seven patients who did not receive such treatment (29% [p = 0.04]/14% [p = 0.03]).

These findings suggest that previously reported data may have overestimated the prognosis of AMKL with t(1;22). Infants aged less than 6 months with severe hepatosplenomegaly demonstrated poor outcomes, and thus AMKL with t(1;22) should be suspected to initiate appropriate chemotherapy immediately.