Prognostic (Risk) Groups
Children's Cancer Group (CCG)/Pediatric Oncology Group (POG) risk groups
Former CCG studies made an initial risk assignment of patients older than 1 year as standard risk or high risk based on the NCI consensus age and WBC criteria, regardless of phenotype. The standard-risk category included patients aged 1 to younger than 10 years who had a WBC count at diagnosis less than 50,000/µL. The remaining patients were classified as high risk. Final treatment assignment for CCG protocols was based on early response to therapy with slow early responders being treated as high-risk patients.
Former POG studies defined the low-risk group based on the NCI consensus age and WBC criteria and required the absence of adverse translocations, absence of CNS disease and testicular disease, and the presence of either the ETV6-RUNX1 translocation or trisomy of chromosomes 4 and 10. The high-risk group required the absence of favorable translocations and the presence of CNS or testicular involvement, or the presence of MLL gene rearrangement, or unfavorable age and WBC count. The standard-risk category included patients not meeting the criteria for inclusion in any of the other risk group categories. In POG studies, patients with T-cell ALL were treated on different protocols than patients with precursor B-cell ALL. The very high-risk category for CCG and POG was defined by one of the following factors taking precedence over all other considerations: presence of the t(9;22), M3 marrow on day 29 or M2 or M3 marrow on day 43, or hypodiploidy (DNA index <0.95).
Children's Oncology Group (COG) risk groups
In COG protocols, children with ALL are initially stratified into treatment groups (with varying degrees of risk of treatment failure) based on a subset of prognostic factors, including the following:
- WBC count at diagnosis.
- Presence of extramedullary disease.
EFS rates exceed 85% in children meeting good-risk criteria (aged 1 to <10 years, WBC count <50,000/μL, and precursor B-cell immunophenotype); in children meeting high-risk criteria, EFS rates are approximately 70%.[3,34,148,155,156] Additional factors, including cytogenetic abnormalities and measures of early response to therapy (e.g., day 7 and/or day 14 marrow blast percentage and MRD levels at the end of induction), considered in conjunction with presenting age, WBC count, and immunophenotype, can identify patient groups with expected EFS rates ranging from less than 40% to more than 95%.[3,104]
Subgroups of patients who have a poor prognosis with current risk-adapted, multiagent chemotherapy regimens may require different therapeutic approaches. For example, infants with ALL are at much higher risk for treatment failure than older children.[10,157] Infants with ALL are generally treated on separate protocols using more intensified regimens, although the likelihood of long-term EFS appears to be no better than 50% for infants with MLL translocations even with a more intensive therapeutic approach.[9,10,11,157] (Refer to the Infants with ALL section of this summary for information about infants with ALL.)