Extramedullary Relapse in Childhood Leukemia

As long-term survival of children with leukemia is increasing, the prophylaxis of extramedullary leukemia has become a more important part of treatment. We studied the pattern of occurrence of extramedullary leukemia in a retrospective review. This review included a total of 2317 childhood leukemia patients aged 15 years or less who had been treated at 38 institutes in Japan between 1976 and 1985. Extramedullary leukemia developed in 386 of 1,724 ALL patients (22.4%) and 63 of 544 patients with ANLL (163%). Among the ALL patients, CNS-L was the most common form and was observed in 315 cases (81.6%), followed by testicular leukemia in 89 (23.0%). In the case of ANLL, the most common form of extramedullary leukemia was CNS-L (45 cases, 71.4%), followed by cutaneous leukemia in 10 cases (15.9%). In addition, leukemia of the lymph nodes, ovaries, bones, kidneys and eyes was observed in 7, 5, 5, 4 and 4 cases, respectively. The survival rate of ALL patients with CNS-L was 40.1% for isolated relapse and 2.7% for bone marrow relapse, and no more deaths occurred after 6 years from relapse. The survival rate of patients with testicular leukemia was 40.1% for isolated relapse and 5.9% for complicating bone marrow relapse, and no deaths occurred after 7 years from relapse. Cutaneous leukemia tended to occur late in older children with ALL and early in infants with ANLL, and all these patients died. Infiltration into the kidney was observed in 4 patients, all of whom died. More than 75% of patients died after isolated relapse of leukemia of the bones, ovaries, lymph nodes and eyes. Prophylactic extramedullary leukemia therapy, of CNS-L in particular, has played an important role in the treatment of childhood leukemia. Careful development of more effective therapy and close observation of late effects are required when monitoring affected children who are still growing.