The main treatment for ALL in adults involves the long-term use of chemotherapy. In the last several years, doctors have begun to use more intensive chemotherapy regimens, which has led to more responses to treatment. But these regimens are also more likely to cause side effects, such as low white blood cell counts. Patients may need to take other drugs to help prevent or treat these side effects.
Treatment typically takes place in 3 phases:
- remission induction
- consolidation (intensification)
- maintenance
The total treatment usually takes about 2 years, with the maintenance phase taking up most of this time. Treatment may be more or less intense, depending on the subtype of ALL and other prognostic factors.
An important part of treatment of ALL is central nervous system (CNS) prophylaxis -- treatment that is meant to ensure the leukemia does not spread to (or remain in) the brain or spinal cord. This is described in more detail below.
Remission induction
The initial phase of chemotherapy usually lasts for a month or so. Different combinations may be used, but they typically include the following drugs:
- vincristine
- dexamethasone or prednisone
- doxorubicin (Adriamycin) or daunorubicin
Based on the patient's prognostic factors, some regimens may also include cyclophosphamide, L-asparaginase, etoposide, and/or high doses of methotrexate or cytarabine (ara-C) as part of the induction phase. For ALL patients who have the Philadelphia chromosome, targeted drugs such as imatinib (Gleevec) are often included as well.
Treatment to keep the leukemia cells from spreading to the CNS is often started at this time. This may include one or more of the following:
- intrathecal chemotherapy (injected directly into the spinal fluid) with methotrexate, and sometimes with cytarabine or a steroid such as prednisone
- high-dose IV methotrexate
- radiation therapy to the brain
Induction chemotherapy can often have serious side effects, including life-threatening infections. For this reason, close monitoring and supportive care with other drugs such as antibiotics is important.
Consolidation (intensification)
If the patient goes into remission, the next phase often consists of fairly short course of chemotherapy, using many of the same drugs that were used for induction therapy. This typically lasts for a few months. Usually the drugs are given in high doses so that the treatment is still fairly intense. CNS prophylaxis may be continued at this time.
Some patients who go into remission are still at high risk for relapse, such as those who have certain subtypes of ALL or other poor prognostic factors. Doctors may suggest an allogeneic stem cell transplant (SCT) at this time, especially for those who have a brother or sister who would be a good donor match. An autologous SCT may be another option. The possible risks and benefits of stem cell transplants need to be weighed carefully, as it's still not clear how helpful they are. Patients considering this procedure may best be served by having it done in the context of a clinical trial at a center that has done a lot of SCT procedures.
Maintenance
After consolidation, the patient is generally put on a maintenance chemotherapy program of methotrexate and 6-mercaptopurine (6-MP). In some cases, this may be combined with other drugs such as vincristine and prednisone. For ALL patients who have the Philadelphia chromosome, targeted drugs such as imatinib (Gleevec) are often included as well. Maintenance usually lasts for about 2 years. CNS prophylaxis may be continued at this time.
Some doctors feel that maintenance therapy may not be needed for some leukemias such as T-cell ALL and mature B-cell ALL (Burkitt leukemia).
Response rates to treatment
In general, about 80% to 90% of adults will have complete remissions after these treatments. That means leukemia cells can no longer be seen in their bone marrow. Unfortunately, about half of these patients relapse, so the overall cure rate is around 30% to 40%. Again, these rates vary depending on the subtype of ALL and other prognostic factors. For example, long-term remission rates tend to be lower in older patients and those whose ALL cells contain the Philadelphia chromosome.
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