Treatment of children with acute promyelocytic leukemia (APL)

Treatment of the M3 subtype of AML (acute promyelocytic leukemia, or APL) differs from usual AML treatment. The leukemia usually responds well to this treatment.

Induction

Many children with APL have blood-clotting problems at the time APL is diagnosed, which can cause serious problems during early treatment. Because of this, children with APL must be treated carefully and are often given an anticoagulant ("blood thinner") to help prevent or treat this.

Along with chemotherapy, children with APL receive a non-chemotherapy drug similar to vitamin A called all-trans retinoic acid (ATRA). A remission can often be induced with ATRA alone, but combining it with chemotherapy (usually daunorubicin and cytarabine) gives better long-term results. APL rarely spreads to the brain or spinal cord, so intrathecal chemotherapy is usually not needed.

Along with the possible side effects from the chemotherapy drugs, ATRA can cause a problem called retinoic acid syndrome. This can include breathing problems from fluid buildup in the lungs, low blood pressure, kidney damage, and severe fluid buildup elsewhere in the body. It can often be treated by stopping the ATRA for a while and giving a steroid such as dexamethasone.

Consolidation (intensification)

This is usually similar to induction, using both ATRA and chemotherapy (usually daunorubicin). Because of the success of this treatment, a stem cell transplant is not usually advised as long as the leukemia stays in remission.

Maintenance

Children with APL may receive maintenance therapy with ATRA (often with the chemo drugs methotrexate and 6-mercaptopurine) for about a year.

Relapsed APL

If the leukemia comes back after treatment, most cases can be put into a second remission. Arsenic trioxide is a drug that is very effective in this setting, although it can sometimes cause problems with heart rhythms. Children getting this drug need to have their blood mineral levels watched closely. ATRA plus chemotherapy may be another option. A stem cell transplant may be considered once a second remission is achieved.