Elvira C. van Dalen

Pharmacogenomic Prediction of Anthracycline-Induced Cardiotoxicity in Children

PURPOSE Anthracycline-induced cardiotoxicity (ACT) is a serious adverse drug reaction limiting anthracycline use and causing substantial morbidity and mortality. Our aim was to identify genetic variants associated with ACT in patients treated for childhood cancer. PATIENTS AND METHODS We carried out a study of 2,977 single-nucleotide polymorphisms (SNPs) in 220 key drug biotransformation genes in a discovery cohort of 156 anthracycline-treated children from British Columbia, with replication in a second cohort of 188 children from across Canada and further replication of the top SNP in a third cohort of 96 patients from Amsterdam, the Netherlands. RESULTS We identified a highly significant association of a synonymous coding variant rs7853758 (L461L) within the SLC28A3 gene with ACT (odds ratio, 0.35; P = 1.8 × 10(-5) for all cohorts combined). Additional associations (P < .01) with risk and protective variants in other genes including SLC28A1 and several adenosine triphosphate-binding cassette transporters (ABCB1, ABCB4, and ABCC1) were present. We further explored combining multiple variants into a single-prediction model together with clinical risk factors and classification of patients into three risk groups. In the high-risk group, 75% of patients were accurately predicted to develop ACT, with 36% developing this within the first year alone, whereas in the low-risk group, 96% of patients were accurately predicted not to develop ACT. CONCLUSION We have identified multiple genetic variants in SLC28A3 and other genes associated with ACT. Combined with clinical risk factors, genetic risk profiling might be used to identify high-risk patients who can then be provided with safer treatment options.

High Risk of Symptomatic Cardiac Events in Childhood Cancer Survivors

PURPOSE To evaluate the long-term risk for validated symptomatic cardiac events (CEs) and associated risk factors in childhood cancer survivors (CCSs). PATIENTS AND METHODS We determined CEs grade 3 or higher: congestive heart failure (CHF), cardiac ischemia, valvular disease, arrhythmia and/or pericarditis (according to Common Terminology Criteria for Adverse Events [CTCAE], version 3.0) in a hospital-based cohort of 1,362 5-year CCSs diagnosed between 1966 and 1996. We calculated both marginal and cause-specific cumulative incidence of CEs and cause-specific cumulative incidence of separate events. We analyzed different risk factors in multivariable Cox regression models. RESULTS Overall, 50 CEs, including 27 cases of CHF, were observed in 42 survivors (at a median attained age of 27.1 years). The 30-year cause-specific cumulative incidence of CEs was significantly increased after treatment with both anthracyclines and cardiac irradiation (12.6%; 95% CI, 4.3% to 20.3%), after anthracyclines (7.3%; 95% CI, 3.8% to 10.7%), and after cardiac irradiation (4.0%; 95% CI, 0.5% to 7.4%) compared with other treatments. In the proportional hazards analyses, anthracycline (dose), cardiac irradiation (dose), combination of these treatments, and congenital heart disease were significantly associated with developing a CE. We demonstrated an exponential relationship between the cumulative anthracycline dose, cardiac irradiation dose, and risk of CE. CONCLUSION CCSs have a high risk of developing symptomatic CEs at an early age. The most common CE was CHF. Survivors treated with both anthracyclines and radiotherapy have the highest risk; after 30 years, one in eight will develop severe heart disease. The use of potentially cardiotoxic treatments should be reconsidered for high-risk groups, and frequent follow-up for high-risk survivors is needed.

Recommendations for Cardiomyopathy Surveillance for Survivors of Childhood Cancer: A Report from the International Late Effects of Childhood Cancer Guideline Harmonization Group

Survivors of childhood cancer treated with anthracycline chemotherapy or chest radiation are at an increased risk of developing congestive heart failure. In this population, congestive heart failure is well recognised as a progressive disorder, with a variable period of asymptomatic cardiomyopathy that precedes signs and symptoms. As a result, several clinical practice guidelines have been developed independently to help with detection and treatment of asymptomatic cardiomyopathy. These guidelines differ with regards to definitions of at-risk populations, surveillance modality and frequency, and recommendations for interventions. Differences between these guidelines could hinder the effective implementation of these recommendations. We report on the results of an international collaboration to harmonise existing cardiomyopathy surveillance recommendations using an evidence-based approach that relied on standardised definitions for outcomes of interest and transparent presentation of the quality of the evidence. The resultant recommendations were graded according to the quality of the evidence and the potential benefit gained from early detection and intervention.

Cardiac function in 5-year survivors of childhood cancer: a long-term follow-up study.

BACKGROUND Childhood cancer survivors (CCSs) have an increased risk of morbidity and mortality. We evaluated the prevalence and determinants of left ventricular (LV) dysfunction in a large cohort of long-term CCSs treated with different potentially cardiotoxic therapies. METHODS The study cohort consisted of all adult 5-year CCSs who were treated with potentially cardiotoxic therapies and who visited our late effects outpatient clinic. Echocardiography was performed in patients who had received anthracyclines, cardiac irradiation, high-dose cyclophosphamide, or high-dose ifosfamide. Detailed treatment data were registered. Both multivariate linear and logistic regression analyses were performed. RESULTS Of 601 eligible CCSs, 525 (87%) had an echocardiogram performed, of which 514 were evaluable for assessment of the LV shortening fraction (LVSF). The median overall LVSF in the whole group of CCSs was 33.1% (range, 13.0%-56.0%). Subclinical cardiac dysfunction (LVSF <30%) was identified in 139 patients (27%). In a multivariate linear regression model, LVSF was reduced with younger age at diagnosis, higher cumulative anthracycline dose, and radiation to the thorax. High-dose cyclophosphamide and ifosfamide were not associated with a reduction of LVSF. Vincristine sulfate was associated with a nonsignificant decrease of cardiac function (P = .07). Epirubicin hydrochloride was as cardiotoxic as doxorubicin when corrected for tumor efficacy, and daunorubicin hydrochloride seemed less cardiotoxic. CONCLUSIONS A high percentage (27%) of young adult CCSs have an abnormal cardiac function. The strongest predictors of subclinical cardiac dysfunction are anthracycline dose, cardiac irradiation, and younger age at diagnosis. There is a suggestion that daunorubicin is less cardiotoxic than other anthracyclines.

A coding variant in RARG confers susceptibility to anthracycline-induced cardiotoxicity in childhood cancer.

Anthracyclines are used in over 50% of childhood cancer treatment protocols, but their clinical usefulness is limited by anthracycline-induced cardiotoxicity (ACT) manifesting as asymptomatic cardiac dysfunction and congestive heart failure in up to 57% and 16% of patients, respectively. Candidate gene studies have reported genetic associations with ACT, but these studies have in general lacked robust patient numbers, independent replication or functional validation. Thus, the individual variability in ACT susceptibility remains largely unexplained. We performed a genome-wide association study in 280 patients of European ancestry treated for childhood cancer, with independent replication in similarly treated cohorts of 96 European and 80 non-European patients. We identified a nonsynonymous variant (rs2229774, p.Ser427Leu) in RARG highly associated with ACT (P = 5.9 × 10−8, odds ratio (95% confidence interval) = 4.7 (2.7–8.3)). This variant alters RARG function, leading to derepression of the key ACT genetic determinant Top2b, and provides new insight into the pathophysiology of this severe adverse drug reaction.

Quality of systematic reviews in pediatric oncology - A systematic review

BACKGROUND To ensure evidence-based decision making in pediatric oncology systematic reviews are necessary. The objective of our study was to evaluate the methodological quality of all currently existing systematic reviews in pediatric oncology. METHODS We identified eligible systematic reviews through a systematic search of the literature. Data on clinical and methodological characteristics of the included systematic reviews were extracted. The methodological quality of the included systematic reviews was assessed using the overview quality assessment questionnaire, a validated 10-item quality assessment tool. We compared the methodological quality of systematic reviews published in regular journals with that of Cochrane systematic reviews. RESULTS We included 117 systematic reviews, 99 systematic reviews published in regular journals and 18 Cochrane systematic reviews. The average methodological quality of systematic reviews was low for all ten items, but the quality of Cochrane systematic reviews was significantly higher than systematic reviews published in regular journals. On a 1-7 scale, the median overall quality score for all systematic reviews was 2 (range 1-7), with a score of 1 (range 1-7) for systematic reviews in regular journals compared to 6 (range 3-7) in Cochrane systematic reviews (p<0.001). CONCLUSION Most systematic reviews in the field of pediatric oncology seem to have serious methodological flaws leading to a high risk of bias. While Cochrane systematic reviews were of higher methodological quality than systematic reviews in regular journals, some of them also had methodological problems. Therefore, the methodology of each individual systematic review should be scrutinized before accepting its results.

Prevalence and risk factors of radiation-induced growth hormone deficiency in childhood cancer survivors: A systematic review

BACKGROUND Growth hormone deficiency (GHD) is usually the first and most frequent endocrine problem occurring after cranial radiotherapy (CRT). The aim of this systematic review was to evaluate the existing evidence of the prevalence and risk factors of radiation-induced GHD in childhood cancer survivors. METHODS MEDLINE, EMBASE and CENTRAL were searched for studies reporting on radiation-induced GHD in childhood cancer survivors. Information about study characteristics, prevalence and risk factors was abstracted and the quality of each study was assessed. A meta-regression analysis was performed. RESULTS The prevalence of radiation-induced GHD was estimated in 33 studies. Most studies had methodological limitations. The prevalence varied considerably between 0% and 90.9%. Selecting only the studies with adequate peak GH cut-off limits (<5 microg/L) resulted in 3 studies. In these studies the prevalence ranged from 29.0% to 39.1%, with a pooled prevalence of 35.6%. Higher CRT dose and longer follow-up time have been suggested to be the main risk factors of GHD by studies included in this review. The meta-regression analysis showed that the wide variation in the prevalence of GHD could be explained by differences in maximal CRT dose. CONCLUSIONS GHD is a frequent consequence after CRT in childhood cancer survivors. The prevalence of radiation-induced GHD ranged from 29.0% to 39.1% when selecting only studies with adequate peak GH cut-off limits. Higher CRT dose and longer follow-up time are the main risk factors. More well-designed studies are needed to accurately estimate the prevalence of GHD and to define the exact CRT threshold dose.

Genetic variants in SLC22A17 and SLC22A7 are associated with anthracycline-induced cardiotoxicity in children.

AIM To identify novel variants associated with anthracycline-induced cardiotoxicity and to assess these in a genotype-guided risk prediction model. PATIENTS & METHODS Two cohorts treated for childhood cancer (n = 344 and 218, respectively) were genotyped for 4578 SNPs in drug ADME and toxicity genes. RESULTS Significant associations were identified in SLC22A17 (rs4982753; p = 0.0078) and SLC22A7 (rs4149178; p = 0.0034), with replication in the second cohort (p = 0.0071 and 0.047, respectively). Additional evidence was found for SULT2B1 and several genes related to oxidative stress. Adding the SLC22 variants to the prediction model improved its discriminative ability (AUC 0.78 vs 0.75 [p = 0.029]). CONCLUSION Two novel variants in SLC22A17 and SLC22A7 were significantly associated with anthracycline-induced cardiotoxicity and improved a genotype-guided risk prediction model, which could improve patient risk stratification.

Management of asymptomatic anthracycline-induced cardiac damage after treatment for childhood cancer: a postal survey among Dutch adult and pediatric cardiologists.

Asymptomatic anthracycline-induced cardiac damage (A-CD) is a serious problem among young childhood cancer survivors. The aim of this survey was to assess the current treatment policy in these patients in the Netherlands. A questionnaire was sent to all 136 departments of adult or pediatric cardiology in the Netherlands. It was returned by 61% of the departments. Sixty-six percent of the respondents started medical treatment (ie, an ACE inhibitor and/or a beta-blocker) in childhood cancer survivors with asymptomatic A-CD. Fifty-eight percent of the respondents indicated that their treatment decision was based on published findings in the literature, but none of them referred to studies evaluating the treatment of asymptomatic A-CD. A majority of adult and pediatric cardiologists started medical treatment in childhood cancer survivors with asymptomatic A-CD without knowledge of the benefits and risks of treatment in this patient group. Before ACE inhibitors and/or beta-blockers can be recommended as routine practice in childhood cancer survivors with asymptomatic A-CD, randomized controlled trials should be performed. Until then, the authors recommend centralizing the treatment of childhood cancer survivors with asymptomatic A-CD in a specialized center to cluster the available knowledge and experience.

Surveillance of hepatic late adverse effects in a large cohort of long-term survivors of childhood cancer: Prevalence and risk factors

BACKGROUND Childhood cancer survivors (CCS) are a growing group of young individuals with a high risk of morbidity and mortality. We evaluated the prevalence and risk factors of hepatic late adverse effects, defined as elevated liver enzymes, in a large cohort of CCS. METHODS The cohort consisted of all five-year CCS treated in the EKZ/AMC between 1966 and 2003, without hepatitis virus infection and history of veno-occlusive disease (VOD). Liver enzyme tests included serum levels of alanine aminotransferase (ALT) for hepatocellular injury and gamma-glutamyltransferase (γGT) for biliary tract injury. We performed multivariable linear and logistic regression analyses. RESULTS The study population consisted of 1404 of 1795 eligible CCS, of whom 1362 performed liver enzyme tests at a median follow-up of 12 years after diagnosis. In total, 118 (8.7%) of 1362 CCS had hepatic late adverse effects defined as ALT or γGT above the upper limit of normal. Abnormal ALT and γGT levels were found in 5.8% and 5.3%, respectively. In multivariable regression analyses treatment with radiotherapy involving the liver, higher body mass index, higher alcohol intake and longer follow-up time were significantly associated with elevated ALT and γGT levels; older age at diagnosis was only significantly associated with elevated γGT levels (all p<0.05). CONCLUSION One in twelve CCS showed signs of hepatic late adverse effects after a median follow-up of 12 years. Several risk factors have been identified. Future studies should focus on the course of long-term liver related outcomes and on the influence of radiotherapy and chemotherapy dose.