Treatment of children with acute lymphocytic leukemia (ALL)
The main treatment for children with acute lymphocytic leukemia (ALL) is chemotherapy, which is usually divided into 3 phases:
- Consolidation (also called intensification)
When leukemia is diagnosed, there are usually about 100 billion leukemia cells in the body. Killing 99.9% of these leukemia cells during the 1-month induction treatment is enough to achieve a remission, but it still leaves about 100 million leukemia cells in the body. These also must be destroyed. An intensive 1- to 2-month program of consolidation treatment and about 2 years of maintenance chemotherapy helps destroy the remaining cancer cells.
As mentioned earlier, children with ALL are typically divided into standard-risk, high-risk, or very high-risk groups to make sure that the correct types and doses of drugs are given. Treatment may be more or less intense, depending on the risk group.
The goal of induction chemotherapy is to achieve a remission. This means that leukemia cells are no longer found in bone marrow samples, the normal marrow cells return, and the blood counts become normal. (A remission is not necessarily a cure.)
More than 95% of children with ALL enter remission after 1 month of induction treatment. This first month is intense and requires prolonged hospital stays for treatment and frequent visits to the doctor. Your child may spend some or much of this time in the hospital, because serious infections or other complications can occur. It is very important to take all medicines as prescribed. Sometimes complications can be serious enough to be life-threatening, but in recent years, advances in supportive care (nursing care, nutrition, antibiotics, red blood cell and platelet transfusions as needed, etc.) have made these much less common than in the past.
Children with standard-risk ALL often receive 3 drugs for the first month of treatment. These include the chemotherapy drugs L-asparaginase and vincristine, and a steroid drug (usually dexamethasone). For children in high-risk groups, a fourth drug in the anthracycline class (daunorubicin is the one most often used) is typically added. Other drugs that may be given early are methotrexate and/or 6-mercaptopurine.
Intrathecal chemotherapy: All children also need chemotherapy into the cerebrospinal fluid (CSF) to kill any leukemia cells that might have spread to the brain and spinal cord. This treatment, known as intrathecal chemotherapy, is given through a lumbar puncture (spinal tap). It is usually given twice (or more if the leukemia is high risk or leukemia cells have been found in the CSF) during the first month and 4 to 6 times during the next 1 or 2 months. It is then repeated less often during the rest of treatment. Usually, methotrexate is the drug used for intrathecal chemotherapy. Hydrocortisone (a steroid) and cytarabine (ara-C) may be added, particularly in high-risk children.
Along with intrathecal therapy, some high-risk patients (for example, those with T-cell ALL) and those with many leukemia cells in their CSF when the leukemia is diagnosed may be given radiation therapy to the brain. This was more common in the past, but recent studies have found that many children even with high-risk ALL may not need radiation therapy if they are given more intensive chemotherapy. Doctors try to avoid giving radiation to the brain if possible, especially in younger children, because no matter how low the dose is kept, it can cause problems with thinking, growth, and development.
A possible side effect of intrathecal chemotherapy is seizures during treatment, which happen in a small percentage of children. Children who develop seizures are treated with drugs to prevent them.
The next, and usually more intense, consolidation phase of chemotherapy typically lasts about 1 to 2 months. This phase reduces the number of leukemia cells still in the body. Several chemo drugs are combined to help prevent the remaining leukemia cells from developing resistance. Intrathecal therapy (as described above) is continued at this time.
Children with standard-risk ALL are usually treated with drugs such as methotrexate and 6-mercaptopurine or 6-thioguanine, but regimens differ among cancer centers. Vincristine, L-asparaginase, and/or prednisone may also be added.
Children with high-risk leukemia generally receive more intense chemotherapy. Extra drugs such as L-asparaginase, doxorubicin (Adriamycin), etoposide, cyclophosphamide, and cytarabine (ara-C) are often used, and dexamethasone
is substituted for prednisone. There may be a second round of intense chemotherapy with the same drugs.
Children with Philadelphia chromosome-positive ALL may benefit from the addition of a targeted drug such as imatinib (Gleevec) or from a stem cell transplant at this time.
If the leukemia remains in remission after induction and consolidation, maintenance therapy can begin. Most treatment plans use daily 6-mercaptopurine and weekly methotrexate, given as pills, often along with vincristine, which is given intravenously, and a steroid (prednisone or dexamethasone). These latter 2 drugs are given for brief periods every 4 to 8 weeks. Other drugs may be added depending on the type of ALL and the risk of recurrence.
During the first few months of maintenance, most treatment plans include 1 or 2 repeat intensified treatments similar to the initial induction. These 4-week intensifications are called re-induction or delayed intensification.
Some children at higher risk may receive more intense maintenance chemotherapy and intrathecal therapy.
The total length of therapy (induction, consolidation, and maintenance) for most ALL treatment plans is 2 to 3 years. Because boys are at higher risk for relapse than girls, many doctors favor giving them several more months of treatment.
Treatment of residual disease
These treatment plans may change if the leukemia doesn’t go into remission during induction or consolidation. The doctor will probably check the child’s bone marrow soon after treatment starts to see if the leukemia is going away. If not, treatment may be more intense or prolonged.
If the leukemia seems to have gone away by standard lab tests, the doctor may do more sensitive tests to look for even small numbers of remaining leukemia cells. If any are found, then chemotherapy again may be intensified or prolonged.