The 5-year survival rate for children and adolescents with acute lymphoblastic leukemia (ALL), the most common childhood cancer, rose from 83.7% for those diagnosed from 1990 to 1994 to 90.4% for those diagnosed from 2000 to 2005, the results of a large, long-term study indicate.
Stephen P. Hunger, MD, of the University of Colorado Cancer Center in Aurora, Colorado, and colleagues analyzed data from 21,626 young people (aged 0 to 22 years) who were enrolled in Children’s Oncology Group (COG) clinical trials from 1990 to 2005. COG includes more than 200 member institutions in the United States, Canada, Australia, and New Zealand; this group of COG trial participants represented 55.8% of ALL cases estimated to have occurred in the United States during that 15-year period in persons younger than 20 years.
In addition to the overall increase in 5-year survival, Hunger’s team found that survival improved significantly in nearly all subgroups of young patients: males and females; children aged 1 to 9 years, aged 10 years and older, and aged 15 years and older; white youths, black youths, and youths of other races; Hispanics, non-Hispanics, and patients of unknown ethnicity; patients with B-cell or T-cell immunophenotype; and patients with National Cancer Institute (NCI) standard-risk or high-risk clinical features.
Infants, adolescents up to 10 years or up to 15 years, patients with T-cell ALL, and patients with NCI high-risk ALL had relative risks of death approximately twofold to eightfold higher than did patients in lower-risk subsets. However, about one-third (36%) of deaths occurred among children with NCI standard-risk features, prompting the investigators to note in their Journal of Clinical Oncology report that efforts to further improve survival must be directed not only toward children in the high-risk subsets but also toward those who are predicted to have an excellent chance for cure.
The only subgroup experiencing no improvement in 5-year survival was that of infants up to 1 year of age (52.1% in 1990-1994 compared with 50.3% in 2000-2005). Although death following relapse or disease progression declined from 43% to 27.2% between the two time periods for infants, the incidence of treatment-related deaths rose from 3.9% to 13.9%. (Their developing immune systems make infants more prone to infection during cancer treatment.)
The development of methotrexate, cytarabine, 6-mercaptopurine, and other ALL drugs raised the 5-year survival rate from less than 10% in the 1960s to approximately 77% between 1985 and 1994. The improved survival seen in the current analysis was explained primarily by an approximate 44% reduction in the risk of death following relapse or disease progression. The ongoing discovery of important biologic subsets of ALL also helped improve survival rates. For example, the addition of imatinib to chemotherapy resulted in a dramatic increase in survival for patients with pediatric Philadelphia chromosome-positive ALL.