Acute lymphoblastic leukemia (ALL)

Seventy-five percent of all children with leukemia have ALL. It is caused by a rapid
proliferation of immature lymphocytes (lymphoblasts), which would normally have
developed into mature T cells or B cells. There are several subgroups of ALL based on
whether the cancer cells developed from precursors of B cells or T cells, or whether
they display characteristics of both.
The first sample of bone marrow taken from the child is analyzed to identify character-
istics of the leukemia cells, in order to help plan the best therapy and predict how the
child will respond to treatment. Different subtypes of leukemia may require different
types of treatment; some can be cured with less chemotherapy, while others require
aggressive treatment to achieve a cure.
I was walking around the hospital looking shell shocked the day after
my daughter was admitted to Children’s Hospital with leukemia. One of
the other mothers came up, introduced herself, and asked what we were
in for. I told her leukemia. She told me that her son had just relapsed
again from a brain tumor. She looked wistful and said how much she
wished that her son had ALL. She said, “You might think that’s strange,
but I see those kids come, get better, and go home. We are still here.”
Prognosis for the child with ALL
Treatment of childhood ALL is one of the major success stories of modern medicine. In
the early 1960s, patients with ALL usually lived only for a few months. In 2001, 75
percent of children receiving optimal treatment were cured. The appropriate treatment
for each child with ALL is determined by analysis of a multitude of features related to
the child and to the leukemia cells. Children who have high-risk disease need more
aggressive treatments than do children with average-risk disease. The following are
some of the factors that doctors consider when determining treatment.
Age
Children ages 1 to 9 typically do better than do infants or older children or teens.
Infants with parts of the MLL gene (at chromosome segment 11q23) rearranged have
a higher risk of relapse than do other infants. More aggressive treatments are usually
needed for infants and children or teens over the age of 9.
White blood count at diagnosis
Children with a WBC count lower than 50,000 per cubic milliliter have a better
prognosis than those with a higher white blood cell count. Most institutions place
children with high white blood counts on more intensive protocols (written plans for
treating disease).
Leukemia cell type
There are two lines of leukemia cells in ALL: B cells and T cells. Some common
antigens (proteins on the surface of the cells) found on B leukemia cells are called
CD19, HLA-DR, and CD10 (cALLa). Eighty to 85 percent of children with ALL have
B-lineage ALL with one or more of these antigens. B-lineage ALL has three levels of
cell maturity that help the doctors decide on the best treatment.
• Early pre-B. About three quarters of children with B-lineage ALL have early
pre-B. This has the best prognosis of all types of ALL.
• Pre-B. Approximately 25 percent of children with pre-B ALL have the t(1;19)
chromosome abnormality (translocation). Although this used to be a poor prog-
nostic factor, with more aggressive modern treatments children with pre-B ALL
appear to fare as well as those with early pre-B leukemia.
• B cell. Approximately 2 percent of children with B-lineage ALL have B cell ALL.
This is the leukemic stage of Burkitt’s lymphoma, and it has a completely different
treatment than other types of ALL.