[Outcome of childhood T-cell acute lymphoblastic leukemia: a report of 99 cases]

To explore the incidence, clinical characteristics and prognosis of childhood T-cell acute lymphoblastic leukemia (T-ALL) enrolled in protocol ALL-2005.

Retrospective reviews of patients diagnosed as having T-ALL were studied in the period between May 2005 and August 2013 in Shanghai Children's Medical Center. Predictive values of early treatment responses, including prednisone response, bone marrow morphology on day 35 during induction chemotherapy, and minimal residual disease (MRD) monitored by flow cytometry on day 35 and 55, were analyzed. The Kaplan-Meier method was used to assess the survival rates.

Ninety-nine evaluable patients aged 1-18 years with newly diagnosed T-ALL were enrolled in protocol ALL-2005. The median follow-up period for patients remaining alive in continuous remission was 60 months (24-109 months). The 5-year event free survival (EFS) and overall survival (OS) rates for these patients were 65% and 69%, respectively. Forty-three (43%) patients were older than 10 years at diagnosis. A total of 61 patients presented with initial white blood cell count (WBC)≥50×10(9)/L. Thirty-seven patients with mediastinal mass were found in this study. Seventy-one patients were defined as prednisone good responders (PGR) on day 8 of prednisone therapy. Ninty-four patients achieved complete remission (CR) on day 35 of induction therapy. MRD negative status (<0.01%) on day 35 were seen in 55% of the 42 assessed patients. MRD negative status on day 55 was seen in 78% of the 52 assessed patients. Patients with high MRD (>1%) on day 55 5-year EFS was 40% were associated with poor prognosis (P=0.03). Early T-cell precursor (ETP) subtype was not associated with treatment outcome in this study. Six patients abandoned therapy, 10 lost to follow-up, 22 had relapsed disease, 1 was diagnosed as having a second tumor and 20 patients died.

Overall outcome for T-ALL on protocol ALL-2005 is favorable. MRD results on day 55 of induction therapy have important prognostic and therapeutic implications.