Postinduction Treatment for Childhood ALL
Standard Postinduction Treatment Options for Childhood ALL
Standard treatment options for consolidation/intensification therapy include the following:
Standard treatment options for maintenance therapy include the following:
Central nervous system (CNS)-directed therapy is provided during premaintenance chemotherapy by all groups. Some protocols (Children’s Oncology Group [COG], St. Jude Children's Research Hospital [SJCRH], and Dana-Farber Cancer Institute [DFCI]) provide ongoing intrathecal chemotherapy during maintenance, while others (Berlin-Frankfurt-Münster [BFM]) do not. (Refer to the CNS-Directed Therapy for Childhood Acute Lymphoblastic Leukemia section of this summary for specific information about central nervous system therapy to prevent CNS relapse in children with ALL who are receiving postinduction therapy.Consolidation/Intensification therapy
Once remission has been achieved, systemic treatment in conjunction with CNS sanctuary therapy follows. The intensity of the postinduction chemotherapy varies considerably depending on risk group assignment, but all patients receive some form of intensification following achievement of remission and before beginning maintenance therapy. Intensification may involve use of the following:
- Intermediate-dose or high-dose methotrexate (1–5 g/m2) with leucovorin rescue or escalating-dose methotrexate without rescue.[1-4]
- Drugs similar to those used to achieve remission (reinduction or delayed intensification).[1,5]
- Different drug combinations with little known cross-resistance to the induction therapy drug combination including cyclophosphamide, cytarabine, and a thiopurine.
- L-asparaginase for an extended period of time.[4,7]
- Combinations of the above.[1,8,9]
In children with standard-risk ALL, there has been an attempt to limit exposure to drugs such as anthracyclines and alkylating agents that may be associated with an increased risk of late toxic effects.[10-12] For example, regimens utilizing a limited number of courses of intermediate-dose or high-dose methotrexate as consolidation followed by maintenance therapy (without a reinduction phase) have been used with good results for children with standard-risk ALL.[2,3,11] Similarly favorable results for standard-risk patients have been achieved with regimens utilizing multiple doses of L-asparaginase (20–30 weeks) as consolidation, without any postinduction exposure to alkylating agents or anthracyclines.[7,13]
Evidence (intensification for standard-risk ALL):
- Clinical trials conducted in the 1980s and early 1990s demonstrated that the use of delayed intensification improved outcome for children with standard-risk ALL treated with regimens using a BFM backbone.[14-16] The delayed intensification phase on such regimens, including those of the COG, consists of a 3-week reinduction (including anthracycline) and reconsolidation containing cyclophosphamide, cytarabine, and 6-thioguanine given approximately 3 months after remission is achieved.[1,14,17]
- A Children's Cancer Group study (CCG-1991/COG-1991) for standard-risk ALL utilized dexamethasone for induction and a second delayed intensification phase. This study also compared escalating intravenous (IV) methotrexate in conjunction with vincristine versus a standard maintenance combination including oral methotrexate given during two interim maintenance phases.[Level of evidence: 1iiDi]
- A second delayed intensification phase provided no benefit in patients who were rapid early responders (M1 marrow on day 7).
- IV methotrexate produced a significant improvement in event-free survival (EFS), which was primarily a result of a decreased incidence of CNS relapse.
In high-risk patients, a number of different approaches have been used with comparable efficacy.[7,19]; [Level of evidence: 2Di] Treatment for high-risk patients generally is more intensive than that for standard-risk patients and typically includes higher cumulative doses of multiple agents, including anthracyclines and/or alkylating agents. Higher doses of these agents increase the risk of both short- and long-term toxicities, and many clinical trials have focused on reducing the side effects of these intensified regimens.
Evidence (intensification for high-risk ALL):
- In a DFCI ALL Consortium trial, children with high-risk ALL were randomly assigned to receive doxorubicin alone (30 mg/m2/dose to a cumulative dose of 300 mg/m2) or the same dose of doxorubicin with dexrazoxane during the induction and intensification phases of multiagent chemotherapy. [20,21]
- The use of the cardioprotectant dexrazoxane prior to doxorubicin resulted in better left ventricular fractional shortening and improved end-systolic dimension Z-scores without any adverse effect on EFS or increase in second malignancy risk compared with the use of doxorubicin alone 5 years posttreatment.
- A greater long-term protective effect was noted in girls compared with boys.
- The former CCG developed an augmented BFM treatment regimen featuring repeated courses of escalating-dose IV methotrexate (without leucovorin rescue) given with vincristine and L-asparaginase during interim maintenance and additional vincristine/L-asparaginase pulses during initial consolidation and delayed intensification. Augmented therapy also included a second interim maintenance and delayed intensification phase.
- In the CCG-1882 trial, National Cancer Institute (NCI) high-risk patients with slow early response (M3 marrow on day 7 of induction) were randomly assigned to receive either standard- or augmented-BFM therapy.
- The augmented therapy regimen in the CCG-1882 trial produced a significantly better EFS than did standard CCG modified BFM therapy.
- In an Italian study, investigators showed that two applications of delayed intensification therapy (protocol II) significantly improved outcome for patients with a poor response to a prednisone prophase.
- The CCG-1961 study used a 2 × 2 factorial design to compare both standard- versus augmented-intensity therapies and therapies of standard duration (one interim maintenance and delayed intensification phase) versus increased duration (two interim maintenance and delayed intensification phases) among rapid early responders.
- Augmented therapy was associated with an improvement in EFS; there was no benefit associated with the administration of the second interim maintenance and delayed intensification phases.[Level of evidence: 1iiA]
- There was a significant incidence of osteonecrosis of bone in teenaged patients who received the augmented-BFM regimen.
- Patients with adverse cytogenetic abnormalities, e.g., t(9;22) or t(4;11).
- Patients with hypodiploidy (<44 chromosomes) and poor response to initial therapy (e.g., high end-induction minimal residual disease [MRD]).
- Patients with high absolute blast count after a 7-day steroid prophase.
- Patients who fail induction therapy, even if they achieve complete remission.
Patients with very high-risk features have been treated with multiple cycles of intensive chemotherapy during the consolidation phase, often including agents not typically used in frontline ALL regimens for standard- and high-risk patients, such as high-dose cytarabine, ifosfamide, and etoposide. However, even with this intensified approach, reported long-term EFS rates range from 30% to 50% for this patient subset.[17,27]
On some clinical trials, very high-risk patients have also been considered candidates for allogeneic stem cell transplantation (SCT) in first remission, [27-29] although it is not clear whether outcomes are better with transplantation.
Evidence (allogeneic SCT in first remission):
- In a European cooperative group study, very high-risk patients (defined as one of the following: morphologically persistent disease after a four-drug induction, t(9;22) or t(4;11), or poor response to prednisone prophase in patients with either T-cell phenotype or presenting white blood cells (WBC) >100,000/μL) were assigned to receive either an allogeneic SCT in first remission (based on the availability of a human lymphocyte antigen–matched related donor) or intensive chemotherapy.
- Using an intent-to-treat analysis, patients assigned to allogeneic SCT (on the basis of donor availability) had a superior 5-year disease-free survival (DFS) than patients assigned to intensive chemotherapy (57% ± 7% for transplant versus 41% ± 3% for chemotherapy, P = .02)
- There was no significant difference in overall survival (OS) (56% ± 6% for transplant versus 50% ± 3% for chemotherapy, P = .12).
- For patients with T- cell ALL and a poor response to prednisone prophase, both DFS and OS rates were significantly better with allogeneic SCT.
- In another study of very high-risk patients that included children with extremely high presenting leukocyte counts and children with adverse cytogenetic abnormalities and/or initial induction failure (M2 marrow [between 5% and 25% blasts]), allogeneic SCT in first remission was not associated with either a DFS or OS advantage.
Backbone of maintenance therapy
The backbone of maintenance therapy in most protocols includes daily oral mercaptopurine and weekly oral or parenteral methotrexate. Clinical trials generally administer oral mercaptopurine in the evening, which is supported by evidence that this practice may improve EFS. On many protocols, intrathecal chemotherapy for CNS sanctuary therapy is continued during maintenance therapy. It is imperative to carefully monitor children on maintenance therapy for both drug-related toxicity and for compliance with the oral chemotherapy agents used during maintenance therapy.
Treating physicians must also recognize that some patients may develop severe hematopoietic toxicity when receiving conventional dosages of mercaptopurine because of an inherited deficiency (homozygous mutant) of thiopurine S-methyltransferase, an enzyme that inactivates mercaptopurine.[32,33] These patients are able to tolerate mercaptopurine only if dosages much lower than those conventionally used are administered.[32,33] Patients who are heterozygous for this mutant enzyme gene generally tolerate mercaptopurine without serious toxicity, but they do require more frequent dose reductions for hematopoietic toxicity than do patients who are homozygous for the normal allele.
Evidence (maintenance therapy):
- In a meta-analysis of randomized trials comparing thiopurines, 6-thioguanine (6-TG) did not improve the overall EFS, although particular subgroups may benefit from its use. The use of continuous 6-TG instead of 6-mercaptopurine (6-MP) during the maintenance phase is associated with an increased risk of hepatic complications, including veno-occlusive disease and portal hypertension.[35-39] Because of the increased toxicity of 6-TG, 6-MP remains the standard drug of choice.
Other approaches to maintenance therapy include the following:
- The Brazilian Childhood Cooperative group reported a variation in approach to maintenance therapy.[Level of evidence: 1A] In a cohort comprising mostly lower-risk children, standard oral versus intermittent IV dosing of methotrexate (weekly vs. every 3 weeks) and 6-MP (daily vs. 10 days on and 11 days off) were compared. Intermittently dosed medications were given at higher doses overall than were standard dosed medications. In addition, boys on the protocol received only 2 years of therapy.
- A significant survival advantage was noted in boys receiving intermittent dosing, while the outcome in girls was equivalent. Because of differences in risk classification and OS rates slightly lower than reported by other groups, it is difficult to know whether the benefits this approach offered to boys would apply in other settings.
- Treatment protocols from the SJCRH previously included an intensified maintenance phase that consisted of rotating pairs of agents, including cyclophosphamide and epipodophyllotoxins, along with more standard maintenance agents.
- A randomized study from Argentina demonstrated no benefit from this intensified approach compared with a more standard maintenance regimen for patients who receive induction and consolidation phases based on a BFM backbone.
- The intensified maintenance with rotating pairs of agents has also been associated with more episodes of febrile neutropenia  and a higher risk of secondary acute myelogenous leukemia, and is no longer used in upfront therapy.
Pulses of vincristine and corticosteroid are often added to the standard maintenance backbone, although the benefit of these pulses within the context of intensive, multiagent regimens remains controversial.
Evidence (vincristine/corticosteroid pulses):
- A CCG randomized trial conducted in the 1980s demonstrated improved outcome in patients receiving monthly vincristine/prednisone pulses. A meta-analysis combining data from six clinical trials from the same treatment era showed an EFS advantage for vincristine/prednisone pulses.[44,45]
- A systematic review of the impact of vincristine plus steroid pulses from more recent clinical trials raised the question of whether such pulses are of value in current ALL treatment, which includes more intensive early therapy.
- In a multicenter randomized trial in children with intermediate-risk ALL being treated on a BFM regimen, there was no benefit associated with the addition of six pulses of vincristine/dexamethasone during the continuation phase, although the pulses were administered less frequently than in other trials in which a benefit had been demonstrated.
- A small multicenter trial of average-risk patients demonstrated superior EFS in patients receiving vincristine plus corticosteroid pulses. In this study, there was no difference in outcome based on type of steroid (prednisone vs. dexamethasone).[Level of evidence: 1iiA]
Evidence (dexamethasone vs. prednisone):
- In a CCG study, dexamethasone was compared with prednisone for children aged 1 to younger than 10 years with lower-risk ALL.[14,48]
- Patients randomly assigned to receive dexamethasone had significantly fewer CNS relapses and a significantly better EFS rate.
- In a Medical Research Council trial, dexamethasone was compared with prednisolone during induction and maintenance therapies in both standard-risk and high-risk patients.
- The EFS and incidence of both CNS and non-CNS relapses improved with the use of dexamethasone.
Maintenance chemotherapy generally continues until 2 to 3 years of continuous complete remission. On some studies, boys are treated longer than girls; on others, there is no difference in the duration of treatment based on gender.[7,17] It is not clear whether longer duration of maintenance therapy reduces relapse in boys, especially in the context of current therapies.[Level of evidence: 2Di] Extending the duration of maintenance therapy beyond 3 years does not improve outcome.Treatment options under clinical evaluation
Risk-based treatment assignment is a key therapeutic strategy utilized for children with ALL, and protocols are designed for specific patient populations that have varying degrees of risk for treatment failure. The Risk-based Treatment Assignment section of this summary describes the clinical and laboratory features used for the initial stratification of children with ALL into risk-based treatment groups.
Ongoing clinical trials include the following:COG studies for B-precursor ALL
- COG-AALL0932 (Risk-Adapted Chemotherapy in Younger Patients With Newly Diagnosed Standard-Risk ALL):
This trial subdivides standard-risk patients into two groups: low risk and average risk. Low risk is defined as the presence of all of the following: NCI-standard risk age/WBC, favorable genetics (e.g., double trisomies or ETV6-RUNX1), CNS1 at presentation, and low MRD (<0.01% by flow cytometry) at day 8 (peripheral blood) and day 29 (marrow). Average risk includes other NCI standard-risk patients excluding those with high day 29 MRD morphologic induction failure or other unfavorable presenting features (e.g., CNS3, iAMP21, low hypodiploidy, MLL translocations, and BCR-ABL).
All patients will receive a three-drug induction (dexamethasone, vincristine, and IV PEG-L-asparaginase) with intrathecal chemotherapy. For postinduction therapy, low-risk patients will be randomly assigned to receive either a regimen based on POG-9404, including six courses of intermediate-dose methotrexate (1 g/m2) but without any alkylating agents or anthracyclines, or a modified BFM backbone including two interim maintenance phases with IV methotrexate and one delayed intensification phase. The objective is not to prove superiority of either regimen, but rather to determine if excellent outcomes (at least 95% 5-year DFS) can be achieved.
All average-risk patients will receive a modified BFM-backbone as postinduction treatment. For these patients, the study is comparing, in a randomized fashion, two doses of weekly oral methotrexate during the maintenance phase (20 mg/m2 and 40 mg/m2) to determine whether the higher dose favorably impacts DFS. Average-risk patients are also eligible to participate in a randomized comparison of two schedules of vincristine/dexamethasone pulses during maintenance (delivered every 4 weeks or every 12 weeks). The objective of this randomization is to determine whether vincristine/dexamethasone pulses can be delivered less frequently without adversely impacting outcome.
- COG-AALL1131 (Combination Chemotherapy in Treating Young Patients With Newly Diagnosed High-Risk ALL):
This protocol is open to patients aged 30 years or younger. Patients treated on this trial are classified as either high risk or very high risk. The presence of any of the following is sufficient to classify a patient as very high risk:
- Age younger than 13 years.
- CNS3 at diagnosis.
- M3 marrow at day 29.
- Unfavorable genetics (e.g., iAMP21, low hypodiploidy, MLL gene rearrangements).
- High marrow MRD (>0.01% by flow cytometry) at day 29 (with the exception of NCI standard-risk patients with favorable genetics).
The high-risk group includes patients aged 10 to 12 years and/or those with WBC count greater than 50,000 who lack very high-risk features, and two groups of NCI standard-risk patients who otherwise lack very high-risk features: (1) those without favorable genetics (no ETV6-RUNX1 or double trisomies 4 and 10), and with day 8 peripheral blood MRD >1%; and (2) those with favorable cytogenetics and with high marrow MRD at day 29. Patients with BCR-ABL (Philadelphia chromosome–positive) are treated on a separate clinical trial.
Patients on this trial will receive a four-drug induction (vincristine, corticosteroid, daunorubicin, and IV PEG-L-asparaginase) with intrathecal chemotherapy. Patients younger than 10 years receive dexamethasone during induction, and those aged 10 years and older receive prednisone. Postinduction therapy consists of a modified BFM backbone, including an interim maintenance phase with high-dose methotrexate and one delayed intensification phase. Very high-risk patients receive a second interim maintenance phase prior to beginning more standard maintenance. Only patients with CNS3 status at diagnosis receive cranial radiation. Those with M3 marrow at day 29 or low hypodiploidy are eligible for allogeneic SCT in first remission.
For high-risk patients, the study will compare, in a randomized fashion, triple intrathecal chemotherapy (methotrexate, cytarabine, and hydrocortisone) with intrathecal methotrexate to determine whether triple intrathecal chemotherapy reduces CNS relapse rates and improves EFS.
For very high-risk patients, the study will test, in a randomized fashion, whether intensified consolidation phases (including either cyclophosphamide/etoposide or clofarabine/cyclophosphamide/etoposide) improves 4-year DFS compared with the standard consolidation phase.
- Total XVI study (TOTXVI) (Total Therapy Study XVI for Newly Diagnosed Patients With ALL): A study at SJCRH is randomly assigning patients to receive either standard-dose (2,500 u/m2) or high-dose (3,500 u/m2) PEG-L-asparaginase during postremission therapy.
- DFCI-11-001 (NCT01574274) (SC-PEG Asparaginase versus Oncaspar in Pediatric ALL and Lymphoblastic Lymphoma): A DFCI ALL Consortium protocol is comparing the pharmacokinetics and toxicity of two forms of IV PEG-L-asparaginase (pegaspargase [Oncaspar] and calaspargase pegol [SC-PEG]). Patients will be randomly assigned to receive a single dose of one of these preparations during multiagent induction, and then either pegaspargase every 2 weeks (15 doses total) or calaspargase pegol every 3 weeks (10 doses total) during the 30-week consolidation phase.
This protocol is also examining the following:
- Whether an intensified consolidation including high-dose cytarabine and etoposide improves the outcome for very high-risk patients (patients with high MRD at the end of remission induction, MLL translocations, or hypodiploidy [<44 chromosomes]).
- Whether antibiotic prophylaxis (with fluoroquinolones) reduces rates of bacteremia and other serious bacterial infections during the remission induction phase.
Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with childhood acute lymphoblastic leukemia in remission. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.
General information about clinical trials is also available from the NCI Web site.References
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