Prospective Study of 168 Infants with Transient Abnormal Myelopoiesis with Down Syndrome: Japan Pediatric Leukemia/Lymphoma Study Group, TAM-10 Study

Introduction: Transient abnormal myelopoiesis (TAM) occurs in approximately 10% of infants with Down syndrome (DS). Although most patients achieve spontaneous remission, some develop severe organ failure and die in their infancy. Previous studies have identified several risk factors associated with early death in such cases, including a high white blood cell (WBC) count, early gestational age, and ascites (Massey GV, 2006; Muramatsu H, 2008; Klusmann JH, 2008). Although chemotherapy with low-dose cytosine arabinoside (LDCA) has been applied for severe cases, its side effect profile has not been fully demonstrated in an adequate number of patients. Here we prospectively analyzed 168 infants with DS who were diagnosed with TAM, including 52 patients treated with LDCA. We assessed the efficacy and safety of LDCA therapy in these cases.

Patient and Methods: Between May 2011 and February 2014, 168 infants (90 boys and 78 girls) were diagnosed with TAM and prospectively registered in the Japan Pediatric Leukemia/Lymphoma Study Group (JPLSG) TAM-10 study. GATA1 gene mutations were identified in all except 7 patients who had a very low blast percentage. The median (range) of WBC count was 38.6 (2.4-478.7) × 10⁹ cells/L, and the median (range) of gestational age was 37 (29-40) weeks. Thirty one (18%) patients developed anasarca at diagnosis, and 23 (14%) patients developed acute megakaryocytic leukemia.

Results: The overall survival (OS) rate and the event-free survival (EFS) rate at 1 year from diagnosis [95% confidential interval (CI)] were 86.3% (80.1-90.7), and 80.2% (73.2-85.5), respectively. Univariate analysis identified the following covariates as risk factors associated with early death (<9 months): early gestational age [<37 weeks; hazard ratio (HR; 95% CI) = 4.482 (1.826-10.997), p = 0.001], parenchymal bleeding [HR (95% CI) = 5.746 (2.241-14.734), p < 0.001], anasarca [HR (95% CI) = 13.344 (5.419-32.860), p < 0.001], and high WBC count [ ≥100 × 10⁹ cells/L; HR (95% CI) = 8.013 (3.354-19.144), p < 0.001]. The multivariate Cox hazard model identified anasarca and a high WBC count (≥100 × 10⁹ cells/L) as independent risk factors for early death. With regard to the 52 patients who received LDCA therapy, only anasarca remained an independent risk factor for early death. Subgroup analysis in patients with a high WBC count (≥100 × 10⁹ cells/L; n = 36) showed that LDCA therapy significantly improved survival [1-year OS (95% CI) = 78.3% (55.4-90.3; n = 23) vs. 38.5% (14.1-62.8; n = 13); p = 0.009]. In contrast, the survival rate of patients with anasarca (n = 31) did not improve on receiving LDCA therapy [1-year OS (95% CI) = 58.3% (27.0-80.1; n = 12) vs. 47.4% (24.4-67.3; n = 19); p = 0.525]. The most common side effect of LDCA was neutropenia (grade 3-4 = 59%), and one patient died due to tumor lysis syndrome.

Conclusion: This prospective study confirmed that a high WBC count and anasarca are risk factors for early death in patients with DS who were diagnosed with TAM. Although LDCA therapy could significantly improve the survival rate in patients with a high WBC count, it failed to change the prognosis of patients with anasarca. A new treatment modality is required for most severe TAM patients with anasarca at diagnosis.