[Clinical features and prognosis of children with acute lymphoblastic leukemia and different platelet levels]

To study the association of platelet level at diagnosis with prognosis in children with acute lymphoblastic leukemia (ALL).

A total of 892 children with ALL who underwent chemotherapy with the CCLG-ALL 2008 regimen were enrolled. According to the platelet count at diagnosis, these children were divided into normal platelet count group (platelet count ≥100×109/L; n=263) and thrombocytopenia group (platelet count <100×10⁹/L; n=629). The thrombocytopenia group was further divided into (50- <100)×10⁹/L (n=243), (20- <50)×10⁹/L (n=263), and <20×10⁹/L (n=123) subgroups. The association of clinical features (sex, age, immunophenotype, and molecular biology) with event-free survival (EFS) and overall survival (OS) was analyzed.

Compared with the thrombocytopenia group, the normal platelet count group had significantly lower positive rate of MLL gene rearrangement and recurrence rate (P<0.05), as well as a significantly higher 10-year EFS rate (P<0.05). There was no significant difference in 10-year OS between the two groups (P>0.05). The normal platelet count group still had a significantly higher 10-year EFS rate than the thrombocytopenia group after the children with MLL gene rearrangement were excluded (P<0.05), and there was still no significant difference in 10-year OS between the two groups (P>0.05). The <20×10⁹/L subgroup had significantly lower 10-year EFS and OS rates than the normal platelet count group, the (50- <100)×10⁹/L subgroup, and the (20- <50)×10⁹/L subgroup (P<0.05). After the children with MLL gene rearrangement were excluded, the <20×10⁹/L subgroup still had significantly lower 10-year EFS and OS rates than the normal platelet count group, the (50-<100)×10⁹/L subgroup, and the (20- <50)×10⁹/L subgroup (P<0.05).

ALL children with MLL gene rearrangement often have the clinical manifestation of thrombocytopenia. Platelet level at diagnosis is associated with the prognosis of ALL children. The children with normal platelet count have a low recurrence rate and good prognosis, and those with a platelet count of <20×10⁹/L have the worst prognosis.