Treatment of the M3 subtype of AML (acute promyelocytic leukemia) differs from usual AML treatment. Most cases respond well to this treatment.
Induction
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. Spread to the brain or spinal cord is very rare with APL, so intrathecal chemotherapy is usually not needed.
The side effects of this treatment differ from those of standard AML induction chemotherapy because of a potential problem called retinoic acid syndrome. This can involve breathing problems due to 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.
During treatment, some children with APL may also develop blood-clotting problems. They may be given an anticoagulant ("blood thinner") to help prevent or treat this.
Consolidation (intensification)
This is usually similar to induction, using both ATRA and chemotherapy (usually daunorubicin). Because of the success of this treatment, stem cell transplant is not usually advised as long as the remission is maintained.
Maintenance
Children with APL may receive maintenance therapy with ATRA (often with the chemotherapy drugs methotrexate and 6-mercaptopurine) for about one 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. A stem cell transplant may be considered once a second remission is achieved.
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