Prognosis and survival for childhood ALL

The following are prognostic factors for childhood acute lymphoblastic leukemia (ALL).

Age at diagnosis is an important prognostic factor for B-cell ALL. Children between the ages of 1 and 10 years have a better prognosis than infants younger than 1 year or children older than 10 years. Children younger than 1 year or older than 10 years have a higher risk that their cancer will not respond to treatment or will come back (recur) after treatment. They often need more intensive treatment.

Age is not a prognostic factor for children with T-cell ALL.

The white blood cell (WBC) count at diagnosis is also called the initial WBC count. It is one of the most important prognostic factors for childhood ALL.

Children with WBC counts less than 50,000 cells/mm³ or 50.0 x 10 ⁹ cells/L have a better prognosis than children with higher WBC counts. Children with higher WBC counts have a higher risk that their cancer will not respond to treatment or will come back after treatment. They often need more intensive treatment.

B-cell ALL has a better prognosis than T-cell ALL.

Chromosome and gene abnormalities in the leukemia cells that are linked with a favourable prognosis include:

• t(12;21)
• having more than 50 chromosomes (called hyperdiploidy)
• DNA index greater than 1.16
• expression of the proteins CD10+, CD19+, HLA-DR+, CD22+ or TdT+
• trisomy (having an abnormal number of chromosomes) 4, 10 or 17

Chromosome and gene abnormalities in the leukemia cells that are linked with an unfavourable prognosis include:

• t(9;22); the Philadelphia chromosome
• t(4;11); MLL gene fusions
• t(1;19)
• having less than 45 chromosomes (called hypodiploidy)
• DNA index less than 0.95
• intrachromosomal amplification of chromosome 21 (iAMP21)

Children with leukemia that has spread to the brain and spinal cord (called the central nervous system, or CNS) at diagnosis have a higher risk that the cancer won’t respond to treatment or will come back after treatment.

Boys with leukemia that has spread to the testicles at diagnosis have a higher risk that the cancer will come back after treatment.

The response to treatment (how well treatment works) in the first 1 to 4 weeks of treatment can predict the cancer’s overall response to treatment. Children whose leukemia responds to treatment by the end of induction chemotherapy are said to have disease in remission. Children with disease in remission have a better prognosis than children whose leukemia does not respond to treatment quickly or who need more than one cycle of chemotherapy to go into remission.

The number of blasts (leukemia cells) in the peripheral blood is called the peripheral blast count. Children with a lower peripheral blast count after 7 days of induction chemotherapy have a more favourable prognosis than children whose peripheral blast count does not go down.

Disease that is still present after treatment but can only be found using more sensitive tests is called minimal residual disease (MRD). Children with detectable MRD at the end of induction therapy have a poorer prognosis than children with no detectable MRD after induction therapy.

Children who are underweight or overweight tend to have a poorer prognosis than children with a normal weight.