Background
Extramedullary leukemia (EML) is common in pediatric acute myeloid leukemia (AML) and occurs as leukemia cells within the cerebrospinal fluid (CSF) or as a solid tumor (myeloid sarcoma-MS). The effect of MS on survival is unknown.
Methods
Patients on CCG protocols 2861, 2891, 2941 and 2961 being treated for AML with intensive-timing chemotherapy were classified for the presence of EML (CSF leukemia, CNS-MS, orbital-MS, or non-CNS MS). CSF leukemia was classified as CNS 3 (≥5 wbc in the CSF with blasts) and non-CSF leukemia as CNS1/2 (<5 wbc in the CSF with or without blasts). Characteristics and outcomes of these patients were compared.
Results
Of the 1459 total patients, 1206(82%) had no EML, 154(11%) had CSF leukemia, 19(1%) had CNS-MS, 23(2%) had orbital-MS, and 57(4%) had non-CNS MS. The CR rate was significantly higher in patients with orbital-MS and CNS-MS than in those with non-MS and non-CNS MS (96% and 95% vs 78% and 78%,p=0.034). Patients with orbital-MS and CNS-MS had significantly higher overall survival than patients with non-CNS MS (92% and 73% vs 38%,p<0.001), CNS3 patients (92% and 73% vs 51,p<0.001), and CNS1/2 patients (92% and 73% vs 50%,p<0.001). Patients with orbital-MS had a significantly lower relapse rate.
Conclusion
Patients with myeloid sarcoma involving orbital and CNS sites had a significantly better survival than patients with non-CNS MS, with CSF leukemia, or with no extramedullary leukemia.