Profile of non-compliance in lymphoblastic leukaemia

Facilitators and barriers to adherence to medical recommendations among adolescents with cancer: A systematic review

We aimed to systematically review barriers/facilitators of adherence among adolescents with cancer (aged 10-24 years), following a comprehensive approach to adherence that goes beyond medication-taking. Empirical studies published in English exploring determinants of adherence to medical recommendations among adolescents with cancer were identified in MEDLINE, PsycInfo, and Web of Science, up to October 2021. Records and full-text articles were reviewed by two independent reviewers, and results were classified according to the World Health Organization's (WHO) multidimensional adherence model. Eighteen studies were included. Despite heterogeneity in the definition and measurement of adherence, literature supported barriers/facilitators at patient, treatment, condition, healthcare team/system, and social/economic levels. Specifically, patient-related factors (i.e., psychological functioning and beliefs about disease and treatment) and social-related factors (i.e., family functioning) were major determinants of adolescent adherence. Few studies were conducted, and inconsistent findings were displayed for other dimensions (i.e., healthcare team/system, treatment, and condition-related factors). Adherence is a complex and multidetermined phenomenon. More research is needed to provide critical insights for policymakers and healthcare professionals in planning practices and interventions that effectively address meaningful barriers/facilitators of adolescents' adherence.

Adherence to Oral Chemotherapy in Acute Lymphoblastic Leukemia during Maintenance Therapy in Children, Adolescents, and Young Adults: A Systematic Review

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children and young adults. Treatment is long and involves 2-3 years of a prolonged maintenance phase composed of oral chemotherapies. Adherence to these medications is critical to achieving good outcomes. However, adherence is difficult to determine, as there is currently no consensus on measures of adherence or criteria to determine nonadherence. Furthermore, there have been few studies in pediatric B-ALL describing factors associated with nonadherence. Thus, we performed a systematic review of literature on oral chemotherapy adherence during maintenance therapy in ALL following PRISMA guidelines. Published studies demonstrated various objective and subjective methods of assessing adherence without generalizable definitions of nonadherence. However, the results of these studies suggested that nonadherence to oral maintenance chemotherapy was associated with increased risk of relapse. Future studies of B-ALL therapy should utilize a uniform assessment of adherence and definitions of nonadherence to better determine the impact of nonadherence on B-ALL outcomes and identify predictors of nonadherence that could yield targets for adherence improving interventions.

Chemotherapy Delays Are Associated with Inferior Outcome in Acute Lymphoblastic Leukemia: A Retrospective Study from a Tertiary Cancer Center in South India

Background Treatment protocols for acute lymphoblastic leukemia (ALL) have evolved over time to give excellent cure rates in children and moderate outcomes in adults; however, little is known how delays in chemotherapy affect long-term survival.

Objectives To find the association of delays during different treatment phases on the survival outcomes.

Materials and Methods Data from 149 ALL cases treated between 2009 and 2015 were retrospectively analyzed. Treatment course in commonly used protocols was divided into three phases—induction, consolidation (postremission), maintenance, and also a combined intensive phase (induction plus consolidation) for the purpose of analysis, and delay in each phase was defined based on clinically acceptable breaks. Analysis was done to find the impact of treatment delay in each phase on the survival outcomes.

Results The median age was 12 years (range, 1–57). Multi-center Protocol-841 (MCP-841) was used for 72%, German Multicenter Study Group for Adult ALL (GMALL) for 19%, and Berlin, Frankfurt, Muenster, 95 protocol (BFM-95) for 9% of patients. Delay in induction was seen in 52%, consolidation in 66%, and during maintenance in 42% of patients. The median follow-up was 41 months, and 3-year survival outcomes for the entire cohort were event-free survival (EFS)—60%, relapse-free survival (RFS)—72%, and overall survival (OS)—68%. On univariate analysis, delay in induction adversely affected EFS (hazard ratio [HR] = 1.78, p = 0.04), while delay in intensive phase had significantly worse EFS and RFS (HR = 2.41 [p = 0.03] and HR = 2.57 [p = 0.03], respectively). On separate analysis of MCP-841 cohort, delay in intensive phase affected both EFS (HR = 3.85, p = 0.02) and RFS (HR = 3.42, p = 0.04), whereas delay in consolidation significantly affected OS with (HR = 4.74, p = 0.04) independently.

Conclusion Treatment delays mostly in intensive phase are associated with worse survival in ALL; attempts should be made to maintain protocol-defined treatment intensity while adequately managing toxicities.

Quantification of Thiopurine Nucleotides in Erythrocytes and Clinical Application to Pediatric Acute Lymphoblastic Leukemia

Background:

Concentrations of 6-thioguanine (6TG) nucleotides and 6-methylmercaptopurine (6MMP) nucleotides in RBCs were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). This assay was validated for clinical use and was applied to blood samples from patients taking mercaptopurine (6MP).

Methods:

RBCs were hemolyzed and deproteinized using perchloric acid, followed by heating for the hydrolysis of nucleotides, and the resultant base was measured using LC-MS/MS. Precision, recovery, linearity, matrix effect, and limit of quantification was validated for clinical application. Our results were compared with another institution's established LC-MS/MS assay. We measured the concentrations of 6TG and 6MMP in RBCs of pediatric patients with acute lymphoblastic leukemia (ALL), and the clinical impact of those metabolites was investigated.

Results:

The imprecision coefficient of variations of 6TG and 6MMP were 5.7%–8.1%, and the bias was within 5%. Lower limits of quantification were set at 54 ng/mL for 6TG and 1036 ng/mL for 6MMP. Correlation coefficients for 6TG and 6MMP were 0.997 and 1.0 in a comparison study. For clinical proof-of-concept, 74 blood samples were collected from 37 pediatric ALL patients receiving maintenance therapy. Concentration of 6TG ranged from 16.1 to 880 pmol/8 × 10⁸ RBCs and that of 6MMP from 55 to 20,937 pmol/8 × 10⁸ RBCs. The 6MP metabolites were not correlated with WBC or absolute neutrophil count. On the other hand, the higher 6MMP level was associated with elevated alanine aminotransferase and aspartate aminotransferase.

Conclusions:

In this study, an assay for the quantification of 6TG and 6MMP in RBCs was established and applied to pediatric ALL patients. Interindividual variability in 6MP metabolite concentrations was considerable and associated with elevation of liver enzymes, which may be useful in the clinical monitoring of 6MP maintenance therapy in pediatric ALL patients.

Adherence to Oral Medications During Maintenance Therapy Among Children and Adolescents With Acute Lymphoblastic Leukemia: A Medication Refill Analysis

Adherence to oral medications during maintenance therapy is essential for pediatric patients with acute lymphoblastic leukemia. Self-reported or electronic monitoring of adherence indicate suboptimal adherence, particularly among particular sociodemographic groups. This study used medication refill records to examine adherence among a national sample of pediatric patients with acute lymphoblastic leukemia. Patients in a national claims database, aged 0 to 21 years with a diagnosis of acute lymphoblastic leukemia and in the maintenance phase of treatment, were included. Medication possession ratios were used as measures of adherence. Overall adherence and adherence by sociodemographic groups were examined. Adherence rates were 85% for 6-mercaptopurine and 81% for methotrexate. Adherence was poorer among patients 12 years and older. Oral medication adherence rates were suboptimal and similar to or lower than previously documented rates using other methods of assessing adherence. Refill records offer a promising avenue for monitoring adherence. Additional work to identify groups most at-risk for poor adherence is needed. Nurses are well positioned to routinely monitor for medication adherence and to collaborate with the multidisciplinary team to address barriers to adherence.

Neuropsychiatric aspects of paediatric brain tumours: an update

The diagnosis and treatment of children and adolescents with cancer has a tremendous and lasting effect on the patients, their families, and other individuals in their social network. It carries a host of psychological and neurobehavioral ramifications, from questions of mortality to changes in levels of functioning in multiple domains. Childhood cancer remains the leading cause of illness-related death in childhood, but significant advances in survival have been made in the past 40 years. This review looks at the neuropsychiatric presentations, psychosocial and treatment-related issues that arise in children with brain tumors.

A systematic review of factors that influence treatment adherence in paediatric oncology patients

WHAT IS KNOWN AND OBJECTIVE

Treatment adherence is an essential component in ensuring best outcomes in the management of paediatric cancers. Compared to the adult population, treatment adherence in the paediatric population is a more complex subject which involves unique dimensions. In this study, we aimed to systematically review the literature to identify factors associated with treatment adherence in the paediatric oncology population.

METHODS

A literature search was carried out using related keywords on electronic databases.

RESULTS AND DISCUSSION

A total of 1036 articles were reviewed, and 39 articles were found to be relevant. A comprehensive review of these articles identified 17 factors that influence adherence. These factors were classified into five major categories: patient-/caregiver-related factors; therapy-related factors; condition-related factors; health system-related factors; and social/economic factors. A baby bear model was proposed to better visualize these five categories that affect treatment adherence, and a framework of questions was designed to help clinicians identify those at risk of non-adherence for early intervention.

WHAT IS NEW AND CONCLUSION

Seventeen factors reviewed were categorized into five main categories, namely patient-/caregiver-related factors, therapy-related factors, condition-related factors, health system factors and social/economic factors, as causes for poor medication adherence in the paediatric oncology population. Clinicians need to be aware that these factors can interact to influence treatment adherence and that some factors may be more relevant in specific contexts (e.g. third world countries, minority groups). The baby bear model is presented to help understand the issues affecting adherence in the paediatric oncology population, and a framework of questions is proposed to help clinicians identify patients at risk of non-adherence.

Improving adherence to oral cancer therapy in clinical practice

Adherence to oral chemotherapy regimens maximizes their effectiveness and minimizes any potential toxicities. Factors specifically related to the treatment, patient, and health care provider may influence medication adherence. Treatment-related factors include the complexity of the regimen, the cost of therapy, the possibility of side effects, and the delay in treatment benefits. Meanwhile, patients may not have an adequate support system or an understanding of the need for the medication, and providers may not fully succeed in communicating the importance of adherence and the types of side effects that may occur. Nonadherence may lead to an increased risk of toxicity, decreased effectiveness, and increased utilization of health care resources. Although various methods for measuring adherence are available, self-reporting is the most widely used. Studies describing adherence in a broad range of cancers are reviewed. Treatment of chronic myeloid leukemia has been revolutionized by the development of oral tyrosine kinase inhibitors that are highly effective in managing the disease when taken consistently. However, nonadherence is relatively common and can lead to reduced rates of response and increased medical costs. Similar effects of nonadherence on outcome and cost have also been observed in patients with various other hematologic malignancies and solid tumors. Interventions to improve adherence to oral chemotherapy regimens include communication about the importance of adherence and the potential consequences of nonadherence, simplification of the patient's medication schedule (if possible), and inclusion of a caregiver or family member in the conversation. Written materials should always be provided to accompany verbal instructions. This review summarizes factors influencing medication adherence, impact of nonadherence on patient outcomes, methods for measuring adherence, previous studies of nonadherence in patients with cancer, common barriers to access, and interventions to improve adherence in the community setting.

Mercaptopurine/Methotrexate maintenance therapy of childhood acute lymphoblastic leukemia: clinical facts and fiction

The antileukemic mechanisms of 6-mercaptopurine (6MP) and methotrexate (MTX) maintenance therapy are poorly understood, but the benefits of several years of myelosuppressive maintenance therapy for acute lymphoblastic leukemia are well proven. Currently, there is no international consensus on drug dosing. Because of significant interindividual and intraindividual variations in drug disposition and pharmacodynamics, vigorous dose adjustments are needed to obtain a target degree of myelosuppression. As the normal white blood cell counts vary by patients' ages and ethnicity, and also within age groups, identical white blood cell levels for 2 patients may not reflect the same treatment intensity. Measurements of intracellular levels of cytotoxic metabolites of 6MP and MTX can identify nonadherent patients, but therapeutic target levels remains to be established. A rise in serum aminotransferase levels during maintenance therapy is common and often related to high levels of methylated 6MP metabolites. However, except for episodes of hypoglycemia, serious liver dysfunction is rare, the risk of permanent liver damage is low, and aminotransferase levels usually normalize within a few weeks after discontinuation of therapy. 6MP and MTX dose increments should lead to either leukopenia or a rise in aminotransferases, and if neither is experienced, poor treatment adherence should be considered. The many genetic polymorphisms that determine 6MP and MTX disposition, efficacy, and toxicity have precluded implementation of pharmacogenomics into treatment, the sole exception being dramatic 6MP dose reductions in patients who are homozygous deficient for thiopurine methyltransferase, the enzyme that methylates 6MP and several of its metabolites. In conclusion, maintenance therapy is as important as the more intensive and toxic earlier treatment phases, and often more challenging. Ongoing research address the applicability of drug metabolite measurements for dose adjustments, extensive host genome profiling to understand diversity in treatment efficacy and toxicity, and alternative thiopurine dosing regimens to improve therapy for the individual patient.

Adherence-related issues in adolescents and young adults with hematological disorders

Nonadherence to medical recommendations is a widespread problem well documented in a multitude of clinical settings. Nonadherence may adversely affect clinical outcomes such as survival and quality of life and increase health-care-related costs. An understanding of the factors driving nonadherence is key to developing effective adherence-enhancing interventions (AEIs). There are ongoing attempts in contemporary adherence research to better define the various components of adherence, to find optimal measures of adherence and correlations with clinical outcomes, and to create a classification system for AEIs. Nonadherence is also widely prevalent among adolescents and young adults (AYAs) with chronic hematological diseases, affecting up to 50% of patients and increasing with age. Combined use of objective (i.e. electronic monitoring, EM) and subjective (i.e. self-report) measures of adherence may be the preferred approach to assess adherence. The unique physical, social and emotional aspects of the AYA life stage are closely related to intricate causes of nonadherence in AYAs such as problems in transition to adult care. Until proven otherwise, the empirical target in AYAs with hematological disorders should be perfect adherence. Multilevel AEIs, EM feedback and behavioral interventions are among the most effective types of AEIs. Despite the magnitude of the problem, only a handful of AEIs have been evaluated among AYAs with hematological disorders. Thus, this is a field with unmet needs warranting high-quality trials using standardized and well-specified assessment methods and interventions. This review discusses the prevalence, definition, causes and clinical implications of nonadherence among AYAs with hematological disorders, along with strategies to measure and improve adherence.

Augmented Berlin-Frankfurt-Münster therapy in adolescents and young adults (AYAs) with acute lymphoblastic leukemia (ALL)

BACKGROUND

Various trials have reported improved outcomes for adolescents and young adults (AYAs) with acute lymphoblastic leukemia (ALL) who received treatment with pediatric-based regimens. Those reports prompted the current investigation of the pediatric augmented Berlin-Frankfurt-Münster (ABFM) regimen in AYA patients. The results were compared with those from a similar population that received the hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone (hyper-CVAD) regimen.

METHODS

Eighty-five patients ages 12 to 40 years who had Philadelphia chromosome (Ph)-negative ALL received the ABFM regimen from October 2006 through April 2012. Their outcome was compared with outcomes in 71 historic AYA patients who received hyper-CVAD from the authors' institution. Patient and disease characteristics, as well as minimal residual disease status, were analyzed for their impact on outcomes.

RESULTS

The complete response rate with ABFM was 94%. The 3-year complete remission duration (CRD) and overall survival (OS) rates were 70% and 74%, respectively. For patients aged ≤21 years, the 3-year CRD and OS rates were 72% and 85%, respectively; and, for patients ages 21 to 40 years, the respective rates were 69% and 60%. The initial white blood cell count was an independent predictive factor of OS and CRD. The minimal residual disease status on days 29 and 84 of therapy also were predictive of long-term outcomes. Severe regimen toxicities included transient hepatotoxicity in 35% to 39% of patients, pancreatitis in 11% of patients, osteonecrosis in 11% of patients, and thrombosis in 22% of patients. The 3-year OS rate was 74% in the ABFM group versus 71% in the hyper-CVAD group, and the corresponding 3-year CRD rate was 70% versus 66%, respectively.

CONCLUSIONS

ABFM was tolerable in AYA patients with ALL but was not associated with significant improvements in CRD and OS compared with hyper-CVAD.

Psychosocial barriers and facilitators to clinical trial enrollment and adherence for adolescents with cancer

Adolescents (aged 15-19 years) have not experienced the same survival gains as children and older adults diagnosed with cancer. Poor clinical trial enrollment and adherence rates among adolescents may account for some of this disparity. Although biological, regulatory, systemic, and practice-related challenges to clinical trial enrollment and adherence have been examined, studies of psychosocial factors, which can serve as barriers or facilitators to enrollment and adherence, are limited. To bring attention to these psychological factors, we reviewed existing literature on psychosocial barriers and facilitators that can affect an adolescent's decision to enroll and adhere to a clinical trial. We also provide potential strategies to address psychosocial factors affecting clinical trial accrual and adherence.

Adherence to leukemia maintenance therapy: a comparative study among children, adolescents, and adults

This study describes patient adherence to leukemia maintenance therapy and the factors associated with nonadherence, with a particular focus on the different age groups concerned. Sixty-four in-depth interviews were performed in three centers among 31 parents of children, 12 parents of adolescents, 12 adolescents, and 9 adult patients. Adherence was determined through a multimethod approach based on patient and/or parent responses to three self-administered questions and patient and/or parent interviews. The results were compared with physician evaluation of adherence. Factors explaining nonadherence were investigated in the in-depth interviews and by statistical analysis of self-administered questionnaires. Intentional nonadherence occurred rarely (4/52 patients, 8%) following poor tolerance of the maintenance therapy. Despite a high motivation to follow the maintenance therapy, repeated forgetfulness (8/52, 15%) was not rare and rarely detected by physicians. Nonadherence increased with age, but also existed among children. Outings, the administration of therapy at bedtime, the lack of monitoring, a low socioeconomic status, and the hepatic side effects of the treatment were also associated with nonadherence. Declared nonadherence of leukemia maintenance therapy is not negligible and should be screened at follow-up consultations using three simple questions.

Analysis of outcomes in adolescents and young adults with chronic myelogenous leukemia treated with upfront tyrosine kinase inhibitor therapy

BACKGROUND

Outcomes in chronic myeloid leukemia have improved with tyrosine kinase inhibitor treatment. However, little is known about outcomes of chronic myeloid leukemia in adolescent and young adult patients.

DESIGN AND METHODS

We reviewed all 468 chronic myeloid leukemia patients treated at our institution with tyrosine kinase inhibitors as initial therapy: imatinib (n=281), nilotinib (n=98) or dasatinib (n=89).

RESULTS

Median age was 47 years, median follow up 71 months and median treatment time with initial tyrosine kinase inhibitors 48 months. Adolescent and young adult was defined as aged 15-29 years. Sixty-one adolescent and young adult patients were identified. The only significant differences between adolescent and young adult and older patients were incidence of splenomegaly and distribution in Sokal risk groups. Only 3 adolescent and young adult patients have died. Rates of complete cytogenetic, major molecular and complete molecular response were significantly higher in older patients compared to adolescent and young adult patients, with a favorable trend in event-free survival for older patients. Transformation-free and overall survival were similar for the two groups.

CONCLUSIONS

The unfavorable trend in outcome for adolescent and young adult patients with chronic myeloid leukemia is unexpected. Additional research in this population is required to better define outcomes, understand the cause of this difference, and to help make better treatment recommendations.

Age span challenges: adherence in pediatric oncology

OBJECTIVES

To review published literature to determine what is known about adherence to oral antineoplastic agents in children with cancer, to identify adherence-related challenges, and to examine the implications of these challenges for clinical practice.

DATA SOURCES

Published literature identified through the MEDLINE, CINAHL, and PsycINFO databases.

CONCLUSION

Oral antineoplastic agents are frequently used in childhood cancer treatment; supportive care regimens for children with cancer also rely heavily on the administration of oral medications. Adherence in pediatric oncology is a complex process involving both parent and child, and requires knowledge and understanding of proper and safe home medication administration in the context of multiple developmental and behavioral concerns that may change over time.

IMPLICATIONS FOR NURSING PRACTICE

Nurses play an important role in adherence by providing patient and family education and psychosocial support targeted to the child's diagnosis, developmental stage, and specifics of the child's treatment regimen.

Psychiatric aspects of pediatric cancer

The diagnosis and treatment of children and adolescents with cancer has a tremendous and lasting effect on the patients, their families, and other individuals in their social network. It carries a host of psychological and behavioral ramifications, from questions of mortality to changes in levels of functioning in multiple domains. In this review the authors address the psychosocial and treatment-related issues that arise in children with cancer, with attention to the adjustment to cancer at different developmental stages, mood and anxiety issues, treatment-related psychiatric sequelae, and the challenges faced by childhood cancer survivors.

A grounded theory of the process of adherence to oral chemotherapy in Hispanic and caucasian children and adolescents with acute lymphoblastic leukemia

Children and adolescents with acute lymphoblastic leukemia (ALL) receive treatment that relies on daily self- or parent/caregiver-administered oral chemotherapy for approximately 2 years. Despite the fact that pediatric ALL is uniformly fatal without adequate treatment, nonadherence to oral chemotherapy has been observed in up to one third of patients. Little is known about the reasons for nonadherence in these patients. This study used Straussian grounded theory methodology to develop and validate a model to explain the process of adherence to oral chemotherapy in children and adolescents with ALL. Thirty-eight semistructured interviews (with 17 patients and 21 parents/caregivers) and 4 focused group discussions were conducted. Three stages were identified in the process of adherence: (a) Recognizing the Threat, (b) Taking Control, and (c) Managing for the Duration. Doing Our Part was identified as the core theme explaining the process of adherence and involves the parent (or patient) taking responsibility for assuring that medications are taken as prescribed. Understanding the association between taking oral chemotherapy and control/cure of leukemia (Making the Connection) appeared to mediate adherence behaviors.

Review of Adherence-Related Issues in Adolescents and Young Adults With Cancer

Purpose

This review aims to provide a broad overview of the issues and clinical challenges of nonadherence in adolescents and young adults (AYAs) with cancer. Nonadherence can reduce treatment efficacy, which places the patient at higher risk of relapse, adverse effects, and poor outcomes.

Design

A review of the English-speaking literature between 1980 and 2008 was conducted to identify relevant publications, which were supplemented by reference and author searches.

Results

Definition and measurement of adherence varies. Most studies have not clearly delineated an AYA age group (ie, 15-25 years) and have been dominated by leukemia and lymphoma samples. Estimates for nonadherence in this population range from 27% to 60%, with openness of family relationships and support found to predict adherence. Strategies to avoid, assess, and manage nonadherence are presented.

Conclusion

Overall, the evidence base for adherence and strategies to promote it in AYAs with cancer is woefully lacking. There is a need for high-quality studies that target clinically important questions, randomized controlled trials of theoretically based interventions, and development and evaluation of training programs for oncology staff in the special issues faced by AYAs with cancer.

Psychiatric aspects of pediatric cancer

The diagnosis and treatment of children and adolescents with cancer has a tremendous and lasting effect on the patients, their families, and other individuals in their social network. It carries a host of psychological and behavioral ramifications, from questions of mortality to changes in levels of functioning in multiple domains. In this review the authors address the psychosocial and treatment-related issues that arise in children with cancer, with attention to the adjustment to cancer at different developmental stages, mood and anxiety issues, treatment-related psychiatric sequelae, and the challenges faced by childhood cancer survivors.

The degree of myelosuppression during maintenance therapy of adolescents with B-lineage intermediate risk acute lymphoblastic leukemia predicts risk of relapse

Drug doses, blood levels of drug metabolites and myelotoxicity during 6-mercaptopurine/methotrexate (MTX) maintenance therapy were registered for 59 adolescents (>or=10 years) and 176 non-adolescents (<10 years) with B-cell precursor acute lymphoblastic leukemia (ALL) and a white blood cell count (WBC) <50 x 10(9)/l at diagnosis. Event-free survival was lower for adolescents than non-adolescents (pEFS(12y):0.71 vs 0.83, P=0.04). For adolescents staying in remission, the mean WBC during maintenance therapy (mWBC) was related to age (r(S)=0.36, P=0.02), which became nonsignificant for those who relapsed (r(S)=0.05, P=0.9). The best-fit multivariate Cox regression model to predict risk of relapse included mWBC and thiopurine methyltransferase activity, which methylates mercaptopurine and reduces the intracellular availability of cytotoxic 6-thioguanine nucleotides (coefficient: 0.11, P=0.02). The correlation of mWBC to the risk of relapse was more pronounced for adolescents (coefficient=0.65, P=0.003) than for non-adolescents (coefficient=0.42, P=0.04). Adolescents had higher mean neutrophil counts (P=0.002) than non-adolescents, but received nonsignificantly lower mercaptopurine and MTX doses during maintenance therapy. Red blood cell MTX levels were significantly related to the dose of MTX among adolescents who stayed in remission (r(S)=0.38, P=0.02), which was not the case for those who developed a relapse (r(S)=0.15, P=0.60). Thus, compliance to maintenance therapy may influence the risk of relapse for adolescents with ALL.

DNA incorporation of 6-thioguanine nucleotides during maintenance therapy of childhood acute lymphoblastic leukaemia and non-Hodgkin lymphoma

PURPOSE

To explore the DNA incorporation of 6-thioguanine nucleotide levels (DNA-6TGN) during 6-mercaptopurine (6MP) therapy of childhood acute lymphoblastic leukaemia (ALL) and non-Hodgkin lymphoma (NHL) and its relation to erythrocyte levels of their metabolites: 6-thioguanine-nucleotides (E-6TGN), methylated metabolites (E-MeMP), Methotrexate polyglutamates (E-MTX), and to thiopurine methyltransferase activity (TPMT).

METHODS

We studied these metabolites in 229 blood samples from 18 children with ALL (N = 16) or NHL (N = 2) on 6MP/Methotrexate maintenance therapy.

RESULTS

DNA-6TGN levels were significantly correlated to E-6TGN (r (p) = 0.66, p = 0.003) with a trend to reach a plateau at high E-6TGN levels. To explore the relative DNA incorporation of 6TGN in relation to cytosol 6TGN levels, a DNA-6TGN index was calculated as DNA-6TGN/E-6TGN. The DNA-6TGN index was inversely correlated to E-6TGN (r (p) = -0.58, p = 0.012), which implies that with increasing levels of E-6TGN relatively less 6TGN are incorporated into DNA. E-MeMP levels were correlated to the DNA-TGN index (r (p) = 0.60, p = 0.008), indicating that high levels of MeMP result in enhanced DNA-6TGN incorporation, possibly due to inhibition of purine de novo synthesis, mediated by some of the methylated 6MP metabolites.

CONCLUSIONS

DNA-6TGN may prove to be a more relevant pharmacokinetic parameter for monitoring 6MP treatment intensity than the previously used erythrocyte 6MP metabolites levels. Prospective clinical trials are needed to evaluate the usefulness of DNA-6TGN for individual dose adjustments.

Chemotherapy-related side effects in childhood acute lymphoblastic leukemia in Indonesia: parental perceptions

Noncompliance with prescribed medication has been associated with increased chance of relapse and poor outcome. Side effects may be an important cause of noncompliance. Fifty-one parents of children with acute lymphoblastic leukemia in a tertiary care hospital in Indonesia were interviewed about their perception of side effects and their impact on treatment noncompliance and daily activities. A symptom checklist assessing 13 common symptoms was used to examine side effects. During chemotherapy, childhood acute lymphoblastic leukemia patients suffered from psychological as well as physical side effects. The most frequent side effect reported by parents was behavior alteration (92%). Second and third in frequency were increased appetite and infections, reported by 88% and 83% of parents, respectively. The most severe side effects were leg weakness, increased appetite, and behavior alteration. The overall frequency of side effects was weakly correlated to noncompliance. Reducing the impact of side effects may increase compliance with the treatment.

Health-care providers' compliance with childhood acute lymphoblastic leukemia protocol in Indonesia

BACKGROUND

Non-compliance with childhood acute lymphoblastic leukemia (ALL) protocol is an important determinant of poor treatment outcome. Non-compliance with protocol may not only concern parents or patients, but may also concern health-care providers (HCP). Our study examines the accuracy of leukemia risk classification and attitude of HCP toward protocol compliance in Indonesia.

PROCEDURE

A combined retrospective study of medical records (MR) and a cross-sectional questionnaire study with HCP were conducted. Accurate ALL risk classification in MR was assessed. HCP' knowledge of risk classification and their attitude toward protocol compliance were examined.

RESULTS

A total of 164 MR patients with ALL were assessed and 97 HCP were interviewed. The protocol criteria for high-risk (HR) were not complete in 82 MR (50%). Of 97 HCP, 95% did not mention all five protocol criteria for HR. Both in the MR as well as in the questionnaires lymphoblast count on day 8 of chemotherapy, as early response to treatment, was the most frequently missed item (missing in 35% of MR and 85% of questionnaires). Only 14% of respondents actually checked with parents whether they administered the prescribed medicines.

CONCLUSIONS

Our study shows that HCP should improve their knowledge and assessment of childhood ALL risk classification, especially lymphoblast count on day 8 of chemotherapy. Proper risk classification and subsequent correct treatment may enable more children to be cured of leukemia.

Current issues in pediatric medication adherence

With the recent emphasis on investigating the efficacy of medication in children, it is also important to assess what determines whether pediatric patients do or do not take their medication. In general, children are no better at adhering to drug therapy than older individuals. Dealing with medication nonadherence is essential given its association with a failure to achieve the desired treatment goal. In addition to the many factors that influence adherence in adults, there are some unique challenges faced in the pediatric age group including the role of family (and its dysfunction), the changes of adolescence, and the lack of appropriate drug formulations. Intervention strategies to improve adherence include behavioral and educational strategies. Although there is no consensus as to what is the best approach to promote adherence with therapy, attention should be given to determining what barriers exist and trying to overcome them by involving children and their parents in the treatment planning process. If possible, the medication regimen, taking into account the frequency and timing of administration, should be tailored to the child and family's lifestyle and daily routine. Consideration should be given to the palatability and formulations of medications prescribed for young children. The use of simplified regimens of better tasting medications and age-appropriate delivery mechanisms may enhance the ability of pediatric patients to adhere to their drug therapy.

Psychosocial issues in adolescents with cancer

Cancer in adolescents is uncommon and when it occurs raises a number of unique challenges for both the patient and their families. Adolescence is a period of time of significant physical and emotional changes and a diagnosis of cancer during this time has a major impact on their psychological and physical development. In this review we will look at the psychosocial issues facing adolescents who have cancer. We will address adolescent development, issues related to informed consent and assent, initial responses to the diagnosis of cancer, quality of life and the experience of the adolescent with cancer, psychological adjustment, support systems, body image issues, sexuality, education, hope, and treatment compliance.

Understanding medication adherence in pediatric acute lymphoblastic leukemia: a review

Significant numbers of children and adolescents with acute lymphoblastic leukemia (ALL) do not adequately adhere to their treatment regimen. Failure to take the appropriate amount of prescribed medication may result in disease relapse. Although a number of research studies have sought to identify the factors associated with medication nonadherence in this group, no systematic study has sought to evaluate the efficacy of intervention packages in improving adherence. The aim of the current paper is to provide an overview of the research investigating treatment adherence in ALL patients and to identify the relevant risk factors associated with reduced adherence with medication. The paper will further discuss the role of psychologic therapy in improving treatment adherence in children and adolescents with ALL, with a particular focus on identifying the need for controlled outcome studies.

How low is too low? Use of cluster analysis to define low levels of mercaptopurine metabolites

BACKGROUND

To group patients receiving treatment for acute lymphoblastic leukemia (ALL) according to their oral mercaptopurine (6-MP) metabolite levels and to establish cut-off points to screen for potential poor clinical outcome.

PROCEDURE

Methodological study using 6-MP metabolite levels from 48 adolescent ALL patients enrolled in a multicenter adherence study. Cluster analysis was the primary analytical technique. We used two validation methods (a split-sampling and a simulation technique) for validating the results.

RESULTS

Four clusters were retained in our initial analysis using our first group of patients (n = 27). Three clusters (labeled 1, 2, and 4) exhibited the expected negative correlation between the two metabolites, that is, "high" values of one were associated with "low" values of the other. One cluster (labeled 3) had "low" levels for both TGN and MMP. Five of the 27 adolescents had their 6-MP "held" during the study. Post-hoc examination of the results revealed that all five grouped in Cluster 3 during the time that their medications were stopped, but grouped in other clusters at other times. The median ANC was highest in Cluster 3, consistent with low therapeutic drug levels. Parameters were reproducible with both validation methods. Values below the respective 75th centile for both TGN and MMP in Cluster 3 for the complete sample (n = 48) are suggested as representing a potentially higher risk for relapse.

CONCLUSIONS

This study provides an objective method for identifying patients at risk for treatment failure due to suboptimal 6-MP therapy; the clinical significance of this approach should be examined in future studies.

The utility of 6-thioguanine metabolite levels in managing patients with inflammatory bowel disease

OBJECTIVES

We aimed at determining the utility of measuring 6-thioguanine (6-TG) and 6-methylmercaptopurine (6-MMP) in inflammatory bowel disease (IBD) patients on azathioprine (AZA) or 6-mercaptopurine (6-MP), whether the described therapeutic range for 6-TG (235-400 pmol/8 x 10(8) red blood cells, RBC) correlated with clinical remission or leukopenia, and if 6-MMP level was a marker for hepatotoxicity (>5,700 pmol/8 x 10(8) RBC).

METHODS

Study eligibility included an IBD diagnosis of >6 months and either active disease or disease remission of <6 months and the use of AZA/6-MP for >10 wk consecutively. Metabolite levels were evaluated against clinical status, CBC, and hepatic parameters.

RESULTS

Seventy-four of 166 AZA/6-MP users were eligible. 6-TG levels >235 pmol/8 x 10(8) RBC were found in 22/59 (38%) with active disease and in 7/15 with remission (47%, p= 0.16). There was a trend of higher 6-TG levels among those in remission versus those with active disease (mean 325 +/- 284 vs 223 +/- 159 pmol/8 x 10(8) RBC, p= 0.2). No hepatotoxicity was observed, although 12.2% had 6-MMP levels > 5,700 pmol/8 x 10(8) RBC. The correlation between 6-MP dose and 6-TG levels was weak (r = 0.22, p= 0.08). The 6-TG level did not correlate with WBC. There were five instances, each of markedly low levels of both 6-TG and 6-MMP, suggesting noncompliance and of marked 6-MMP levels versus 6-TG.

CONCLUSIONS

There was a poor correlation between 6-TG levels and remission. Nonetheless, the measurements of these levels are helpful when patients are on high doses but not achieving remission since noncompliance or metabolism favoring 6-MMP can be established.

Clinical and laboratory evaluation of compliance in acute lymphoblastic leukaemia

AIM

To evaluate compliance in children with acute lymphoblastic leukaemia (ALL).

METHODS

Compliance was assessed through specific interviews, annotations from medical charts, and erythrocytic determination of 6-mercaptopurine metabolites.

RESULTS

A total of 39 patients who had concluded maintenance phase of chemotherapy were included in the study. Mothers were responsible for delivering 6-MP in 87% of cases. Thirty five interviewees said that medical prescription was well understood and that the main reason for non-compliance was forgetfulness. Non-compliance was detected through interviews (33.3% of the cases), reports from medical charts (30.7%), and drug determination (16.6%); 53.8% of children were found to be non-compliant. Non-compliance was significantly associated with chronic undernourishment. Although not statistically significant, there was a trend for the group of non-compliant children to be associated with low per capita family income. No significant associations of non-compliance with age at diagnosis, gender, parents' schooling level, number of family members, power consumption, and medians of absolute leucocyte or neutrophil blood counts were detected. A short follow up period precluded valid analysis on outcome. In the non-compliant group (n = 21), seven children relapsed, contrasting with three relapses in the compliant group (n = 18).

CONCLUSIONS

Results suggest that non-compliance is one of the mechanisms which underlies the adverse influence of socioeconomic factors on the outcome of children with ALL. Additional studies are necessary to confirm this hypothesis. Comprehensive approaches to the problem of non-compliance are urgently needed.

An improved HPLC method for the quantitation of 6-mercaptopurine and its metabolites in red blood cells

A procedure is described for the rapid determination of the intra-erythrocyte concentration of 6-mercaptopurine (6-MP) and its metabolites, 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine (6-MMP). Erythrocytes (8 x 10(8) cells) in 350 microl Hanks solution containing 7.5 mg dithiothreitol were treated with 50 microl 70% perchloric acid. The precipitate was removed by centrifugation (13,000 g) and the supernatant hydrolyzed at 100 degrees C for 45 min. After cooling, 100 microl was analyzed directly by HPLC using a Radialpack Resolve C18 column eluted with methanol-water (7.5:92.5, v/v) containing 100 mM triethylamine. 6-TG, 6-MP and the hydrolysis product of 6-MMP, 4-amino-5-(methylthio)carbonyl imidazole, were monitored at 342, 322 and 303 nm using a Shimadzu SPD-M10A diode array UV detector. The analytes eluted at 5.3, 6.0 and 10.2 min, respectively. The calibration curves were linear (r(2) > 0.998), and the analytical recoveries were 73.2% for 6-TG, 119.1% for 6-MP and 97.4% for 6-MMP. The intra- and inter-assay variations were highest for 6-MP (9.6 and 14.3%, respectively). The lowest detectable concentrations were 3, 3 and 25 pmol/8 x 10(8) erythrocytes for 6-TG, 6-MP and 6-MMP, respectively. The quantification limits (coefficients of variation <15%) were 8, 10 and 70 pmol/8 x 10(8) erythrocytes for 6-TG, 6-MP and 6-MMP, respectively. The method was applied to the analysis of 183 samples from 36 children under chemotherapy for acute lymphoblastic leukemia. The concentrations of the metabolites in the red cells of the patients ranged from 0 to 1934 pmol/8 x 10(8) erythrocytes for 6-TGN, and from 0 to 105.8 and 0 to 45.9 nmol/8 x 10(8) erythrocytes for 6-MP and 6-MMP, respectively. The procedure gave results that were in agreement with those obtained with other methods designed to detect cases of non-compliance with treatment, including patient interviews and medical evaluation, among others, demonstrating its applicability to monitoring the treatment of leukemic children.

Cancer in adolescents and young adults: treatment and outcome in Victoria

OBJECTIVES

To describe the location of treatment, recruitment to clinical trials and outcomes for adolescents and young adults treated for cancer in Victoria.

DESIGN AND SETTING

Retrospective review of all adolescents and young adults aged 10-24 years diagnosed with cancer between 1992 and 1996, identified from the Victorian Cancer Registry.

MAIN OUTCOME MEASURES

Treatment regimen (clinical trial, treatment protocol or neither), compliance with treatment and 5-year survival.

RESULTS

Questionnaires were completed for 576 of 665 eligible adolescents and young adults (87% response rate). Recruitment into clinical trials decreased with increasing age. Adolescents aged 10-19 years were more likely to be recruited to a clinical trial if treated at a paediatric hospital. For all cancers, 5-year survival was similar across the age groups and was not influenced by the place of treatment. Only 1% of adolescents and young adults failed to complete planned therapy due to non-compliance.

CONCLUSIONS

Despite a similar incidence of cancer to that in younger children, adolescents and young adults with cancer are poorly recruited into clinical trials in Victoria. Establishment of a cancer resource network in Victoria may provide information to both paediatric and adult oncologists about currently available clinical trials.

Intensification of mercaptopurine/methotrexate maintenance chemotherapy may increase the risk of relapse for some children with acute lymphoblastic leukemia

PURPOSE

Thioguanine nucleotides (TGNs) mediate the cytotoxicity of mercaptopurine (MP). Methylated MP metabolites (formed by thiopurine methyltransferase [TPMT]) and methotrexate (MTX) polyglutamates can inhibit de novo purine synthesis. We explored whether dose adjustment of MP and MTX by erythrocyte (E) levels of TGN and MTX (including polyglutamates) could improve outcome in childhood acute lymphoblastic leukemia (ALL).

PATIENTS AND METHODS

A total of 538 children with ALL were randomly assigned to have their oral MP/MTX maintenance therapy adjusted by white cell counts (WBC), E-TGN, and E-MTX (pharmacology group), or by WBC only (control group).

RESULTS

After a median follow-up of 7.8 years, 79 patients had relapsed. Cox regression analysis showed an increased risk of relapse for boys (P =.00003), high WBC at diagnosis (P =.03), pharmacology arm (6.6 times increased relapse hazard for girls), high TPMT activity (P =.002), and high average neutrophil counts during maintenance therapy (P =.0009), with a significant interaction between sex and randomization group (P =.0007). For girls, the relapse risk was 5% in the control group and 19% in the pharmacology group (P =.001) because of an increased relapse hazard during the first year after cessation of therapy. TPMT activity was the most significant predictor of relapses among girls in the pharmacology arm (P <.0001). Overall, the TPMT activity was higher for patients who relapsed after cessation of therapy compared with those who stayed in remission (girls 19.5 v 17.4 U/mL, P =.03; boys 19.3 v 18.0 U/mL, P =.04).

CONCLUSION

Adding pharmacologically guided treatment intensification to dose adjustments by blood counts may not be warranted for girls, whereas new approaches to optimize maintenance therapy are needed for boys.

Oral chemotherapy agents in the treatment of leukaemia

Oral chemotherapy agents have been an important component of the treatment of leukaemia for many years. Obstacles such as poor or erratic bioavailability and noncompliance have often limited the utility of oral agents in the treatment of leukaemia. However, recent evaluations of new or existing oral agents have expanded the clinician's options and understanding of the use of these drugs in the treatment of leukaemia. One major advance is the use of tretinoin (all-trans retinoic acid) in the treatment of acute promyelocytic leukaemia (APL). Tretinoin, an oral vitamin A derivative that reverses abnormal differentiation in APL is now an essential component of first-line therapy for APL, replacing standard intravenous chemotherapy induction regimens. Other advances include an increased understanding of the pharmacokinetic and pharmacodynamic profile of oral chemotherapy agents such as etoposide and high dose busulfan, allowing for modifications or individualisation of administration regimens to enhance efficacy or minimise toxicity. Evaluations of noncompliance with oral agents in the treatment of leukaemia have also provided the clinician with important information on how this obstacle to oral therapy may be overcome or minimised.

Pediatric Acute Lymphoblastic Leukemia: Challenges and Controversies in 2000

This article discusses ways in which pediatric patients with acute lymphoblastic leukemia (ALL) can be stratified to receive intensive and less intensive therapies in order to decrease morbidity and mortality. Specifically, the focus may shift away from current intensive therapies for ultra low-risk patients and away from transplantation for certain patients at relapse. In contrast, infants with ALL comprise an ultra high-risk population in need of specialized approaches.

In Section I Dr. Lange describes the need to identify ultra low-risk children. Groups around the world have improved the outcome of children with ALL by identifying the basic “total therapy” model of the 1970s and stratifying treatment according to risk of relapse. Current first-line treatment cures about 85% of children with standard-risk ALL and 70% of children with high-risk disease. However, all children receive anthracyclines, alkylating agents, or moderate- to high-dose antimetabolite infusions. While randomized clinical trials prove that these intensifications reduce relapses, they also show that half of all children with ALL can be cured with the modest therapy of the 1970s and early 1980s. The patients curable with lesser therapy may be considered an ultra low-risk group. Attempts to use age, gender, white count, morphology, and karyotype to identify the ultra low-risk group of patients with a 90-95% cure rate with minimal therapy have failed. An expanded repertoire of tools such as pharmacogenetic profiling, PCR measurement of minimal residual disease and microarray technology may make this goal achievable in this decade.

In section II Dr. Chessells addresses the management of children with relapsed ALL. The chance of successful re-treatment with conventional chemotherapy for relapse depends on the duration of first remission and the site of relapse. Bone marrow transplantation from a histocompatible sibling or other suitable donor, which is widely accepted as the treatment of choice for children with a first remission of &lt; 24 months, is associated with a high risk of relapse. Bone marrow transplantation for later bone marrow relapse improves leukemia-free survival but has significant short-term and long-term toxicities. The challenges are to develop more effective treatment for early relapse and to identify those children with relapsed ALL who are curable with chemotherapy or, failing this, those children who would be candidates for bone marrow transplantation in third remission.

In Section III Dr. Felix addresses the problem of infant ALL. ALL of infancy is clinically aggressive, and infants continue to have the worst prognosis of all pediatric patients with ALL. High white blood cell count, younger age, bulky extramedullary disease, and CNS disease at diagnosis are unfavorable characteristics. These features occur with MLL gene translocations. The probability of an MLL gene translocation and the probability of poor outcome both are greatest in younger infants. Specialized intensive chemotherapy approaches and bone marrow transplantation in first remission for this disease may lead to improved survival.

Refined recognition of pediatric patients with ALL who need more and less intensive therapies is necessary to increase survival and decrease toxicities.

Pediatric Acute Lymphoblastic Leukemia: Challenges and Controversies in 2000

This article discusses ways in which pediatric patients with acute lymphoblastic leukemia (ALL) can be stratified to receive intensive and less intensive therapies in order to decrease morbidity and mortality. Specifically, the focus may shift away from current intensive therapies for ultra low-risk patients and away from transplantation for certain patients at relapse. In contrast, infants with ALL comprise an ultra high-risk population in need of specialized approaches.

In Section I Dr. Lange describes the need to identify ultra low-risk children. Groups around the world have improved the outcome of children with ALL by identifying the basic “total therapy” model of the 1970s and stratifying treatment according to risk of relapse. Current first-line treatment cures about 85% of children with standard-risk ALL and 70% of children with high-risk disease. However, all children receive anthracyclines, alkylating agents, or moderate- to high-dose antimetabolite infusions. While randomized clinical trials prove that these intensifications reduce relapses, they also show that half of all children with ALL can be cured with the modest therapy of the 1970s and early 1980s. The patients curable with lesser therapy may be considered an ultra low-risk group. Attempts to use age, gender, white count, morphology, and karyotype to identify the ultra low-risk group of patients with a 90-95% cure rate with minimal therapy have failed. An expanded repertoire of tools such as pharmacogenetic profiling, PCR measurement of minimal residual disease and microarray technology may make this goal achievable in this decade.

In section II Dr. Chessells addresses the management of children with relapsed ALL. The chance of successful re-treatment with conventional chemotherapy for relapse depends on the duration of first remission and the site of relapse. Bone marrow transplantation from a histocompatible sibling or other suitable donor, which is widely accepted as the treatment of choice for children with a first remission of < 24 months, is associated with a high risk of relapse. Bone marrow transplantation for later bone marrow relapse improves leukemia-free survival but has significant short-term and long-term toxicities. The challenges are to develop more effective treatment for early relapse and to identify those children with relapsed ALL who are curable with chemotherapy or, failing this, those children who would be candidates for bone marrow transplantation in third remission.

In Section III Dr. Felix addresses the problem of infant ALL. ALL of infancy is clinically aggressive, and infants continue to have the worst prognosis of all pediatric patients with ALL. High white blood cell count, younger age, bulky extramedullary disease, and CNS disease at diagnosis are unfavorable characteristics. These features occur with MLL gene translocations. The probability of an MLL gene translocation and the probability of poor outcome both are greatest in younger infants. Specialized intensive chemotherapy approaches and bone marrow transplantation in first remission for this disease may lead to improved survival.

Refined recognition of pediatric patients with ALL who need more and less intensive therapies is necessary to increase survival and decrease toxicities.

Mercaptopurine therapy intolerance and heterozygosity at the thiopurine S-methyltransferase gene locus

BACKGROUND

Patients with acute lymphoblastic leukemia are often treated with 6-mercaptopurine, and those with homozygous deficiency in thiopurine S-methyltransferase (TPMT) enzyme activity have an extreme sensitivity to this drug as a result of the accumulation of higher cellular concentrations of thioguanine nucleotides. We studied the metabolism, dose requirements, and tolerance of 6-mercaptopurine among patients with different TPMT phenotypes.

METHODS

We compared, by use of statistical modeling, 6-mercaptopurine pharmacology and tolerance in 180 patients who achieved remission on St. Jude Children's Research Hospital Protocol Total XII composed of weekly methotrexate (40 mg/m(2)) and daily oral 6-mercaptopurine (75 mg/m(2)) given for 2.5 years, interrupted every 6 weeks during the first year for treatment with either high-dose methotrexate or teniposide plus cytarabine. Statistical tests were two-sided.

RESULTS

Erythrocyte concentrations of thioguanine nucleotides (pmol/8 x 10(8) erythrocytes) were inversely related to TPMT enzyme activity (P<.01), with averages (+/- standard deviations) of 417 (+/-179), 963 (+/-752), and 3565 (+/-1282) in TPMT homozygous wild-type (n = 161), heterozygous (n = 17), and homozygous-deficient (n = 2) patients, respectively. There was complete concordance between TPMT genotype and phenotype in a subset of 28 patients for whom TPMT genotype was determined. There were no sex differences in thioguanine nucleotide concentrations (P =.24), TPMT enzyme activity (P =.22), or average weekly prescribed dose of 6-mercaptopurine (P=.49). The cumulative incidence of 6-mercaptopurine dose reductions due to toxicity was highest among patients homozygous for mutant TPMT (100%), intermediate among heterozygous patients (35%), and lowest among wild-type patients (7%) (P<.001), with average (+/- standard deviation) final weekly 6-mercaptopurine doses of 72 (+/-60), 449 (+/-160), and 528 (+/-90) mg/m(2), respectively. Lowering doses of 6-mercaptopurine in TPMT heterozygotes and in deficient patients allowed administration of full protocol doses of other chemotherapy while maintaining high thioguanine nucleotide concentrations.

CONCLUSION

We conclude that genetic polymorphism in TPMT is an important determinant of mercaptopurine toxicity, even among patients who are heterozygous for this trait.

Metabolites of mercaptopurine in red blood cells: a relationship between 6-thioguanine nucleotides and 6-methylmercaptopurine metabolite concentrations in children with lymphoblastic leukemia

Intracellular concentrations of 6-mercaptopurine metabolites, i.e. of 6-thioguanine nucleotides (6-TGN) and of 6-methylmercaptopurine metabolites (6-mMP) were analysed in red blood cells (RBC) of 19 children with acute lymphoblastic leukemia (ALL), the subjects of a maintenance chemotherapy of their first remission. Interpatient variations in concentrations of both metabolites were high; concentrations of 6-TGN varied from <60 to 833 pmol/8x10(8) RBC (median value, 144) and those of 6-mMP metabolites from <150 to 19000 pmol/8x10(8) RBC (median value, 3250). In two patients, 6-TGN appeared at concentrations below the limits of assay sensitivity, and 6-mMP metabolites were not detected. In another child the concentrations of both metabolites were at the limit of the assay sensitivity. In three other children the concentrations of both metabolites were below the median value of the group. In the analysed group of children, significant correlations were found between the white cell count (WBC) and RBC 6-TGN (r(s)=-0.72, P<0. 005) as well as between the neutrophil count and RBC 6-TGN (r(s)=-0.60, P<0.01). No significant correlation was found between the concentrations of 6-TGN and 6-mMP metabolites. The monitoring of concentrations of 6-TGN as well as of 6-mMP metabolites allows an early identification of patients who are at an increased risk of the disease relapse as indicated by the low levels of either 6-TGN itself or of its two metabolites.