The survival rate of childhood acute lymphoblastic leukemia (ALL) has reached >80-90% in developed countries, which is a triumph of modern medicine. This success is due to implementation of contemporary treatment protocols, optimal application of risk stratification, risk-directed multi-agent chemotherapy regimens, and improved supportive care. Unfortunately, such improvements have not translated to Low Middle Income Countries (LMICs), where 90% of the world's children live. The estimated 5 year survival rates in Asia range widely between 44.3% and 80%. The Intercontinental-BFM2002 study, conducted in 15 upper-middle and high-income countries reported a 5 year event-free survival (EFS) and overall survival (OS) rates of 74% and 82%, respectively. Factors that may contribute to the lower survival in LMICs are highly complex, including delays in presentation, diagnostic inaccuracy, restricted budget for risk-stratification and appropriate treatment, treatment abandonment and socio economic status.
In Malaysia, different protocols are used by different leukemia treatment centers for treating children with ALL. In UKM Medical Centre (UKMMC), the UKALL protocols (modified UK X, XI, XII, 97(99) and 2003) have been used in the Pediatric Hemato-Oncology Unit since the 1990s. Herein, we report the adopted protocol, the stratification profile and outcome of children with ALL, treated with modified UKALL 97(99) and UKALL 2003 in our institution from 2006 to 2014.
Clinical data from children with ALL, who received these modified therapies, were retrospectively reviewed. Prednisolone was used in modified UKALL97(99) and Dexamethasone in modified UKALL 2003, while 6-mercaptopurine was used in both modified protocols. Otherwise, chemotherapy and duration of treatment were identical to the original protocols of Regimens A, B and C. ALL was diagnosed based on standard morphology and immunophenotyping criteria. At diagnosis, patients were stratified according to the National Cancer Institute (NCI) risk criteria and using FISH for detection of cytogenetic abnormalities. EFS and OS were determined using the Kaplan-Meier methods.
Newly diagnosed ALL in 156 children were included in the study; 103 (66.0%) were standard risk, 49 (31.4%) were high risk and 4 (2.5%) were infants. There were 2 children with Down syndrome. The success rate of FISH was 76.4% (94/123). Patients were stratified as standard risk, based on ETV6-RUNX1, and high risk based on unfavorable cytogenetics, BCR-ABL and MLL rearrangements. Half of the patients with unfavorable cytogenetics were classified in the NCI high risk group, with WCC >100x109/L. A total of 151 patients were treated as per risk stratification, 2 patients transferred care, while 3 patients refused treatment. Mortality from sepsis during treatment was approximately 10%, including 2 deaths during induction remission and induction at relapse.
The majority of disease progression was relapse-related, however, treatment abandonment also contributed to relapse. Approximately 5% of patients abandoned their treatment (3 patients abandoned and 3 patients refused treatment). The 5-year OS for the standard risk group was 86.6%, with 3-year and 5-year EFS of 88.1% and 83.4%, respectively. The 5-year OS for the high risk group was 65.7%, while 3-year and 5-year EFS were 64.7% and 58.2%, respectively (Figure 1). The MRC UKALL97 stratification by NCI risk reported a 5-year EFS of 83.1% for the standard risk group and 66.9% for the high risk group, while the UKALL2003 interim analysis reported a 5-year EFS of 87.7%. The MRC UKALL97/99 reported a 5-year OS of 88%.
The cure rate of children with standard risk ALL at UKMMC, using modified UKALL 97(99) and UKALL 2003 protocols, was comparable to MRC UKALL97. However, the cure rate for high risk ALL was comparatively lower. This single center study from UKMMC has highlighted some critical factors that improved the outcome of children with ALL and suggests further improvements that are necessary to reduce the relapse rate, especially in the high risk ALL patients.
No relevant conflicts of interest to declare.
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