The treatment of acute promyelocytic leukemia (APL) differs from other forms of AML. Children with APL have leukemic cells with a gene swap (translocation) between chromosomes 15 and 17.
Since these children respond well to therapy, the treatment is usually less intense than other types of AML. However, the medicines needed for treatment will affect healthy cells inside your child’s bone marrow, making them prone to infections and bleeding. For this reason, children with APL need to stay in the hospital during the first 10 days to 2 weeks of their first treatment phase (induction therapy). This way, the treatment team can carefully monitor your child for any infection, bleeding, or other complications.
Standard risk APL
Standard risk APL is diagnosed when the initial white blood cell count of the patient is less than 10,000/mm3 in the blood.
Chemotherapy for standard risk APL is divided into two separate phases. The purpose of each phase is to destroy as many leukemia cells as possible. Each phase differs in length and requires specific medicines.
1. Induction phase
The aim of induction therapy is to destroy leukemic cells and get your child into remission.
Your child is in remission when:
- less than 5% of the bone marrow cells are cancerous (on the microscope)
- the bone marrow is producing a normal amount of white blood cells, red blood cells and platelets (small cells that help stop bleeding at sites of the body that are cut or injured).
Children with APL undergo one cycle of induction therapy, which lasts between 28 to 60 days. The length of the cycle depends on the response to treatment, which is evaluated by a bone marrow exam on Day 29.
Medicines taken during induction therapy
During induction therapy, your child will take:
- all-trans-retinoic acid (ATRA), orally (by mouth)
- arsenic trioxide (ATO), through an IV (intravenous catheter) line
2. Consolidation phase
Even when in complete remission, your child may still have some leukemic cells inside their bone marrow that doctors cannot see under the microscope. To treat the undetectable cancer cells, your child undergoes more cycles of chemotherapy in a second consolidation phase. This phase is also important to prevent the disease from returning.
Generally, doctors treat your child with four cycles of consolidation therapy. Each cycle lasts 8 weeks.
Medicines taken during the consolidation phase
During the consolidation phase, your child will take:
- ATRA, orally
- ATO, through an IV
High-risk APL
A patient is diagnosed with high-risk APL when their initial white blood cell count is 10,000/mm3 or more.
Chemotherapy for high-risk APL is divided into three separate phases. Each phase is a different length and requires specific medicines. The purpose of each phase is to destroy as many leukemia cells as possible.
1. Induction phase
The aim of induction therapy is to destroy leukemic cells and get your child into remission.
Your child is in remission when:
- less than 5% of the bone marrow cells are cancerous
- the bone marrow is producing a normal amount of white blood cells, red blood cells and platelets.
Children with high-risk APL undergo one cycle of induction therapy, which lasts about 36 days.
Medicines taken during induction therapy
During induction therapy, your child will take:
- ATRA, orally
- ATO, through an IV
- Idarubicin (chemotherapy) through an IV
2. Consolidation phase
Even when in complete remission, your child may still have some leukemic cells inside their bone marrow that doctors cannot see on the microscope. These cells would be discovered in a positive PCR test. To treat these cancer cells, your child would have more cycles of chemotherapy in a consolidation phase. This phase is important to prevent the disease from returning.
Generally, doctors treat your child with two cycles of consolidation therapy. Consolidation cycle 1 lasts for 28 days and cycle 2 lasts for 35 days.
Medicines taken during the consolidation phases
- ATRA, orally
- ATO, IV
3. Maintenance phase
This phase lasts for about two years. In maintenance phase, there are no detectable leukemic cells in your child’s bone marrow or blood. At this point, a PCR test would be negative.
The aim of this phase is to prevent the disease from returning and kill any leukemic cells that we cannot identify through a microscope or PCR.
Medicines taken during maintenance phase
During maintenance, your child will take these medicines by mouth:
- ATRA
- mercaptopurine (6-MP)
- methotrexate (MTX)
They will take 6-MP every night and MTX once a week until the end of maintenance. Every three months, they will also take ATRA for 15 consecutive days.
Lumbar punctures are not included in the treatment plan for APL unless the brain and spinal fluid had been involved at diagnosis.
Your child will have to come to the hospital outpatient clinic to:
- have blood-work done to check complete blood count (CBC) every 2 to 4 weeks and liver function tests every 3 months
Blood work is important because doctors need to make sure that the amount of your child’s white blood cells (neutrophils or Polys) are not too high or too low. If they are too low, then the chemotherapy is killing too many marrow cells, making your child neutropenic and at risk for developing an infection. If the amount of neutrophils is too high, then the therapy is not killing enough hidden leukemia cells. For this reason, making sure your child takes their medicines without missing doses is essential to keep your child in remission and reduce the risk of relapse.
How can you help your child keep a healthy lifestyle during maintenance?
During maintenance, your child needs to maintain a healthy lifestyle. Encourage your child to eat nutritious food and to participate in daily exercise. Physical activity is very important to maintain good health and also minimize your child’s risk of becoming obese, which can be a long-term side-effect of the treatment. Typically there are no restrictions on physical activity during maintenance chemotherapy. Talk to the treatment team to discuss your child’s physical activity options.
For more information, please see Good Nutrition During Leukemia Treatment.