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PURPOSE A previous study by the International Berlin-Frankfurt-Münster Study Group (I-BFM-SG) on childhood KMT2A-rearranged ( KMT2A-r) AML demonstrated the prognostic value of the fusion partner. This I-BFM-SG study investigated the value of flow cytometry-based measurable residual disease (flow-MRD) and evaluated the benefit of allogeneic stem-cell transplantation (allo-SCT) in first complete remission (CR1) in this disease. METHODS A total of 1,130 children with KMT2A-r AML, diagnosed between January 2005 and December 2016, were assigned to high-risk (n = 402; 35.6%) or non–high-risk (n = 728; 64.4%) fusion partner-based groups. Flow-MRD levels at both end of induction 1 (EOI1) and 2 (EOI2) were available for 456 patients and were considered negative (RESULTS The high-risk group had inferior EFS (30.3% high risk v 54.0% non-high risk; P < .0001), CIR (59.7% v 35.2%; P < .0001), and OS (49.2% v 70.5%; P < .0001). EOI2 MRD negativity was associated with superior EFS (n = 413; 47.6% MRD negativity v n = 43; 16.3% MRD positivity; P < .0001) and OS (n = 413; 66.0% v n = 43; 27.9%; P < .0001), and showed a trend toward lower CIR (n = 392; 46.1% v n = 26; 65.4%; P = .016). Similar results were obtained for patients with EOI2 MRD negativity within both risk groups, except that within the non–high-risk group, CIR was comparable with that of patients with EOI2 MRD positivity. Allo-SCT in CR1 only reduced CIR (hazard ratio, 0.5 [95% CI, 0.4 to 0.8]; P = .00096) within the high-risk group but did not improve OS. In multivariable analyses, EOI2 MRD positivity and high-risk group were independently associated with inferior EFS, CIR, and OS. CONCLUSION EOI2 flow-MRD is an independent prognostic factor and should be included as risk stratification factor in childhood KMT2A-r AML. Treatment approaches other than allo-SCT in CR1 are needed to improve prognosis.

Purpose: To evaluate the prevalence of and risk factors for hypertension in childhood cancer survivors (CCSs) who were treated with potentially nephrotoxic therapies.Methods: In the Dutch Childhood Cancer Survivor Study LATER cohort part 2 renal study, 1024 CCS ≥5 years after diagnosis, aged ≥18 years at study participation, treated between 1963 and 2001 with nephrectomy, abdominal radiotherapy, total body irradiation (TBI), cisplatin, carboplatin, ifosfamide, high-dose cyclophosphamide (≥1 g/m2 per single dose or ≥10 g/m2 total) or haematopoietic stem cell transplantation participated and 500 controls from Lifelines. Hypertension was defined as blood pressure (BP) (mmHg) systolic ≥140 and/or diastolic ≥90 or receiving medication for diagnosed hypertension. At the study visit, the CKD-EPI 2012 equation including creatinine and cystatin C was used to estimate the glomerular filtration rate (GFR). Multivariable regression analyses were used.For ambulatory BP monitoring (ABPM), hypertension was defined as BP daytime: systolic ≥135 and/or diastolic ≥85, night time: systolic ≥120 and/or diastolic ≥70, 24-h: systolic ≥130 and/or diastolic ≥80. Outcomes were masked hypertension (MH), white coat hypertension and abnormal nocturnal dipping (aND).Results: Median age at cancer diagnosis was 4.7 years (interquartile range, IQR 2.4–9.2), at study 32.5 years (IQR 27.7–38.0) and follow-up 25.5 years (IQR 21.4–30.3). The prevalence of hypertension was comparable in CCS (16.3%) and controls (18.2%). In 12% of CCS and 17.8% of controls, hypertension was undiagnosed. A decreased GFR (2) was associated with hypertension in CCS (OR 3.4, 95% CI 1.4–8.5). Risk factors were abdominal radiotherapy ≥20 Gy and TBI. The ABPM-pilot study (n = 77) showed 7.8% MH, 2.6% white coat hypertension and 20.8% aND.Conclusion: The prevalence of hypertension was comparable among CCS who were treated with potentially nephrotoxic therapies compared to controls, some of which were undiagnosed. Risk factors were abdominal radiotherapy ≥20 Gy and TBI. Hypertension and decreased GFR were associated with CCS. ABPM identified MH and a ND.

Introduction: The number of children surviving cancer in Africa is increasing. Knowledge about late effects of survivors is lacking. Our study maps literature regarding late effects of childhood cancer survivors in Africa. Methods: Scoping review was performed following JBI-guidelines. Systematic literature search was conducted in: Medline, Embase, African Index Medicus, Web of Science, Scopus, Psycinfo. Titles and abstracts were screened by two reviewers, followed by full-text analysis by the lead reviewer. Results: Sixty-eight studies were included for content analysis. Studies originated from 10 of 54 African countries. Most studies had retrospective study design, 2–5 years follow-up, solely chemotherapy as treatment modality, Egypt as country of origin. Fifty-three studies described physical, and seventeen studies described psychosocial late effects. Conclusion: Literature concerning late effects is available from a limited number of African countries. Psychosocial domain lacks attention compared to the physical domain. More countries should report on this topic to prevent, identify and monitor late effects.

A heatmap generated using K-means clustering of expression of VEGF-A associated genes; LG-BSG samples (blue) in the disease type histology (upper legends) cluster with normal brain (purple). DIPG (red) clusters with GBM (green). DIPG (green), pHGG/GBM (red).

Supplemental Figure 2: VEGF mRNA expression in DIPG in comparison to normal brain (n=31) as analyzed by R2 (R2.amc.nl), clustered by stage of disease; unknown (n=10), pretreatment (n=2) and postmortem (n=23)

Purpose:Diffuse intrinsic pontine glioma (DIPG) is an incurable type of pediatric brain cancer, which in the majority of cases is driven by mutations in genes encoding histone 3 (H3K27M). We here determined the preclinical therapeutic potential of combined AXL and HDAC inhibition in these tumors to reverse their mesenchymal, therapy-resistant, phenotype.Experimental Design:We used public databases and patient-derived DIPG cells to identify putative drivers of the mesenchymal transition in these tumors. Patient-derived neurospheres, xenografts, and allografts were used to determine the therapeutic potential of combined AXL/HDAC inhibition for the treatment of DIPG.Results:We identified AXL as a therapeutic target and regulator of the mesenchymal transition in DIPG. Combined AXL and HDAC inhibition had a synergistic and selective antitumor effect on H3K27M DIPG cells. Treatment of DIPG cells with the AXL inhibitor BGB324 and the HDAC inhibitor panobinostat resulted in a decreased expression of mesenchymal and stem cell genes. Moreover, this combination treatment decreased expression of DNA damage repair genes in DIPG cells, strongly sensitizing them to radiation. Pharmacokinetic studies showed that BGB324, like panobinostat, crosses the blood–brain barrier. Consequently, treatment of patient-derived DIPG xenograft and murine DIPG allograft-bearing mice with BGB324 and panobinostat resulted in a synergistic antitumor effect and prolonged survival.Conclusions:Combined inhibition of AXL and HDACs in DIPG cells results in a synergistic antitumor effect by reversing their mesenchymal, stem cell-like, therapy-resistant phenotype. As such, this treatment combination may serve as part of a future multimodal therapeutic strategy for DIPG.

Purpose: Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive pediatric brain tumor, for which no effective therapeutic options currently exist. We here determined the potential of inhibition of the maternal embryonic leucine zipper kinase (MELK) for the treatment of DIPG.Experimental Design: We evaluated the antitumor efficacy of the small-molecule MELK inhibitor OTSSP167 in vitro in patient-derived DIPG cultures, and identified the mechanism of action of MELK inhibition in DIPG by RNA sequencing of treated cells. In addition, we determined the blood–brain barrier (BBB) penetration of OTSSP167 and evaluated its translational potential by treating mice bearing patient-derived DIPG xenografts.Results: This study shows that MELK is highly expressed in DIPG cells, both in patient samples and in relevant in vitro and in vivo models, and that treatment with OTSSP167 strongly decreases proliferation of patient-derived DIPG cultures. Inhibition of MELK in DIPG cells functions through reducing inhibitory phosphorylation of PPARγ, resulting in an increase in nuclear translocation and consequent transcriptional activity. Brain pharmacokinetic analyses show that OTSSP167 is a strong substrate for both MDR1 and BCRP, limiting its BBB penetration. Nonetheless, treatment of Mdr1a/b;Bcrp1 knockout mice carrying patient-derived DIPG xenografts with OTSSP167 decreased tumor growth, induced remissions, and resulted in improved survival.Conclusions: We show a strong preclinical effect of the kinase inhibitor OTSSP167 in the treatment of DIPG and identify the MELK–PPARγ signaling axis as a putative therapeutic target in this disease. Clin Cancer Res; 24(22); 5645–57. ©2018 AACR.

Supplemental legend

List of off-target effects of OTSSP167 occurring at concentrations lower than 50nM, derived from the publicly available phosphoproteomics database at http://proteomicsdb.org.

MELK mRNA expression during embryonic central nervous system development, derived from the Brainspan atlas.

Legends pertaining to supplementary figures and tables

File containing all supplementary figures

Sequences of shRNA constructs used in the present study.

Pediatric acute myeloid leukemia (pAML) is typified by high relapse rates and a relative paucity of somatic DNA mutations. Although seminal studies show that splicing factor mutations and mis-splicing fuel therapy-resistant leukemia stem cell (LSC) generation in adults, splicing deregulation has not been extensively studied in pAML. Herein, we describe single-cell proteogenomics analyses, transcriptome-wide analyses of FACS-purified hematopoietic stem and progenitor cells followed by differential splicing analyses, dual-fluorescence lentiviral splicing reporter assays, and the potential of a selective splicing modulator, Rebecsinib, in pAML. Using these methods, we discover transcriptomic splicing deregulation typified by differential exon usage. In addition, we discover downregulation of splicing regulator RBFOX2 and CD47 splice isoform upregulation. Importantly, splicing deregulation in pAML induces a therapeutic vulnerability to Rebecsinib in survival, self-renewal, and lentiviral splicing reporter assays. Taken together, the detection and targeting of splicing deregulation represent a potentially clinically tractable strategy for pAML therapy.

Vincristine is a well-established cytotoxic drug. In paediatric populations blood collection via venipuncture is not always feasible. Volumetric absorptive microsampling (VAMS) is a less invasive method for blood collection. Furthermore, VAMS lacks the haematocrit effect on the recovery known with dried blood spots. Therefore, a liquid chromatography tandem-mass spectrometry method was developed and validated for the quantification of vincristine in whole blood collected with VAMS devices. Sample preparation consisted of solid-liquid extraction with 0.2% formic acid in water and acetonitrile. The final extract was injected on a C18 column (2.0 ×50 mm, 5 µm). Gradient elution was used and quantification was accomplished with a triple quadruple mass spectrometer operating in the positive mode. The validated concentration range was from 1 to 50 ng/mL with an intra- and inter-accuracy and precision of ± 10.3% and ≤ 7.3%, respectively. This method was able to successfully quantify vincristine concentrations in whole blood collected with VAMS from paediatric oncology patients. Vincristine concentrations in whole blood were non-linearly associated with plasma concentrations, which could be described with a saturable binding equilibrium model.

Background: Pediatric acute myeloid leukemia (AML) is a challenging disease to treat in low- and middle-income countries (LMICs). Literature suggests that survival in LMICs is poorer compared with survival in high-income countries (HICs). Aims: This study evaluates the outcomes of Kenyan children with AML and the impact of sociodemographic and clinical characteristics on outcome. Methods and Results: A retrospective medical records study was performed at Moi Teaching and Referral Hospital (MTRH) in Eldoret, Kenya, between January 2010 and December 2018. Sociodemographic and clinical characteristics, and treatment outcomes were evaluated. Chemotherapy included two “3 + 7” induction courses with doxorubicin and cytarabine and two “3 + 5” consolidation courses with etoposide and cytarabine. Supportive care included antimicrobial prophylaxis with cotrimoxazole and fluconazole, and blood products, if available. Seventy-three children with AML were included. The median duration of symptoms before admission at MTRH was 1 month. The median time from admission at MTRH to diagnosis was 6 days and to the start of AML treatment 16 days. Out of the 55 children who were started on chemotherapy, 18 (33%) achieved complete remission, of whom 10 (56%) relapsed. The abandonment rate was 22% and the early death rate was 46%. The 2-year probabilities of event-free survival and overall survival were 4% and 7%, respectively. None of the sociodemographic and clinical characteristics were significantly associated with outcome. Conclusion: Survival of Kenyan children with AML is dismal and considerably lower compared with survival in HICs. Strategies to improve survival should be put in place including better supportive care, optimization of the treatment protocol, and reduction of the abandonment rate and time lag to diagnosis with sooner start of treatment.

The administration of high-dose methotrexate (HD-MTX) requires an accurate monitoring of blood MTX levels to determine the regimen of leucovorin rescue and urine alkalinization to prevent toxicity. However, it is technically and logistically challenging to screen patients routinely in limited-resource settings. This study aimed to evaluate blood MTX levels at 24- and 48-hours from start of infusion in relation to clinical toxicity in childhood ALL. Methods: A prospective cohort study was conducted on 32 consecutive children with acute lymphoblastic leukemia (ALL) who had received at least one cycle of 1 g/m2 HD-MTX intravenous infusion as a part of consolidation treatment based on the 2013 Indonesian ALL Protocol. In total, 68 cycles were evaluated. Serum MTX concentrations were measured using enzyme immunoassay. MTX toxicity was categorized using common toxicity criteria (CTCAE) 3.0 version. The association between MTX level and clinical toxicity was assessed by non-parametric analysis. Results: The 24-hours MTX level was median 29.8 ng/mL (0.065 µmol/L) (IQR 8.1–390.6) with a modest decrease in 48-hours MTX serum level in all cycles (median 28.3 ng/mL and 0.062 µmol/L; IQR 0.35–28.7; p

Summary Glucocorticoids form the backbone of paediatric acute lymphoblastic leukaemia (ALL) treatment. Many studies have been performed on steroid resistance; however, few studies have addressed the relationship between dose, concentration and clinical response. The aim of the present study was to evaluate the pharmacokinetics of prednisolone in the treatment of paediatric ALL and the correlation with clinical parameters. A total of 1028 bound and unbound prednisolone plasma concentrations were available from 124 children (aged 0–18 years) with newly diagnosed ALL enrolled in the Dutch Childhood Oncology Group studies. A population pharmacokinetic model was developed and post hoc area under the curve (AUC) was tested against treatment outcome parameters. The pharmacokinetics of unbound prednisolone in plasma was best described with allometric scaling and saturable binding to proteins. Plasma protein binding decreased with age. The AUC of unbound prednisolone was not associated with any of the disease parameters or treatment outcomes. Unbound prednisolone plasma concentrations correlated with age. No effect of exposure on clinical treatment outcome parameters was observed and does not substantiate individualised dosing. Poor responders, high‐risk and relapsed patients showed a trend towards lower exposure compared to good responders. However, the group of poor responders was small and requires further research.

Background: Although survival rates for retinoblastoma (RB) are over 95% in high-income countries, its high mortality rate in low and middle-income countries remains a great concern. Few studies investigated treatment outcome and factors contributing to RB survival in these latter settings. Aims of this study are to determine treatment outcome of Indonesian children diagnosed with RB and to explore factors predictive of treatment outcome. Methods: This study was a retrospective medical records review combined with an illustrative case report. Children newly diagnosed with RB between January 2011 and December 2016 at a tertiary care referral hospital in Indonesia were included. A home visit was conducted to perform an in-depth interview with a mother of two children affected by RB. Results: Of all 61 children with RB, 39% abandoned treatment, 21% died, 20% had progressive or relapsed disease and 20% event-free survival. Progressive or relapsed disease was more common in older (≥ 2 years at diagnosis, 29%) than young (

Introduction: Survival rates of pediatric acute myeloid leukemia (AML) in low- and middle-income countries (LMICs) seem extremely poor, and the available literature on the matter is scarce. Accordingly, there is a limited understanding of poor treatment outcomes seen in this population. Areas covered: We provide an overview of the available literature with respect to treatment outcomes of pediatric AML in LMICs yielding poor outcomes compared to high-income countries. Moreover, treatment outcomes vary markedly between LMICs. In addition, there is a wide variation among studies in how treatment outcomes are reported and analyzed. Expert opinion: The substantially inferior treatment outcomes of pediatric AML in LMICs emphasize the unprecedented importance of global initiatives and international collaborations to improve the survival of these patients. A coordinated approach is necessary to carry out country-specific situational analyses. These analyses will result in operational plans on how to structurally implement childhood cancer registries, align healthcare infrastructure, build on capacities, and provide universal health coverage in LMICs. In addition, we strongly recommend that, in the future, LMICs document, analyze, and publish pediatric AML treatment outcomes in a more structured and uniform manner.

Purpose To assess the impact of maintenance therapy and the additional impact of dexamethasone treatment on cancer-related fatigue and sleep-wake rhythms in pediatric acute lymphoblastic leukemia (ALL) patients and to determine the association between these outcomes. Methods A national cohort of pediatric ALL patients (≥ 2 years) was included (± 1 year post-diagnosis). Patients receiving dexamethasone were assessed twice (assessment with and without dexamethasone). Actigraphy assessments were used to calculate sleep-wake outcomes with nonparametric methods. Cancer-related fatigue was assessed with the PedsQL Multidimensional Fatigue Scale. Sleep-wake rhythms and cancer-related fatigue were compared between patients participating in the assessment without dexamethasone and healthy children (linear regression) and between assessments with and without dexamethasone (mixed models). Using linear regression, associations between sleep-wake outcomes and cancer-related fatigue were determined during assessments with and without dexamethasone. Results Responses were collected for 125 patients (113 assessments with and 81 without dexamethasone). The sleep-wake rhythm was less stable (p = 0.03) and less robust (p = 0.01), with lower physical activity levels (p p p = 0.001) and cancer-related fatigue more severe (p ≤ 0.001) during assessments with dexamethasone compared to without dexamethasone. Sleep-wake outcomes were significantly associated with cancer-related fatigue during periods without dexamethasone, but not during periods with dexamethasone. Conclusion Sleep-wake rhythms are disturbed, physical activity levels lower, and cancer-related fatigue levels higher during maintenance therapy. Interventions aimed to enhance sleep-wake rhythms during maintenance therapy could improve cancer-related fatigue. Families should be supported in coping with the additional burden of dexamethasone treatment to improve well-being of ALL patients.

Introduction: For many cancers, adolescent and young adult (AYA) patients have a poorer prognosis than pediatric patients. This study compares long-term survival outcomes of children and AYAs diagnosed with acute myeloid leukemia (AML) in the Netherlands. This has not been done before despite the availability of high-quality data collected by the nationwide, population-based Netherlands Cancer Registry (NCR). Methods: Data on all AML patients aged 0-39 years, diagnosed between 1990-2015, were obtained from the NCR (N=2058). Relative (disease-specific) survival was estimated for all patients, children (0-17 years), and AYAs (18-39 years) using the traditional cohort approach. Early mortality was defined as death within 30 days of diagnosis. Multivariable analyses were performed using generalized linear models (excess mortality) and logistic regression (early mortality). Results: The prognosis of Dutch AML patients below the age of 40 years has improved considerably during the past decades with 5-year relative survival rates increasing from 39% in 1990-1999 to 61% in 2010-2015 (p trend When compared to children, the excess risk of dying due to AML was 70% higher in AYAs [95% confidence interval (95% CI), 47%-97%] after adjustment for follow-up time, sex, period of diagnosis, and stem cell transplantation. The excess hazard ratios (HRs) of mortality were 2.0 (95% CI, 1.6-2.4) for 18-29 year olds and 2.1 (95% CI, 1.7-2.6) for 30-39 year olds, using 1-9 year olds as reference. Early mortality declined over time from 9% to 4% (p trend Conclusions: AYAs diagnosed with AML in the Netherlands between 1990 and 2015 had a worse prognosis than pediatric patients. The survival disparity seemed most evident in recent years, suggesting that improvements in care resulting in better outcome for children have not led to equal benefits for AYAs yet. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Existing drug delivery methods have not led to a significant increase in survival for patients with malignant primary brain tumors. While the combination of conventional therapies consisting of surgery, radiotherapy, and chemotherapy has improved survival for some types of brain tumors (e.g., WNT medulloblastoma), other types of brain tumors (e.g., glioblastoma and diffuse midline glioma) still have a poor prognosis. The reason for the differences in response can be largely attributed to the blood–brain barrier (BBB), a specialized structure at the microvasculature level that regulates the transport of molecules across the blood vessels into the brain parenchyma. This structure hampers the delivery of most chemotherapeutic agents for the treatment of primary brain tumors. Several drug delivery methods such as nanoparticles, convection enhanced delivery, focused ultrasound, intranasal delivery, and intra-arterial delivery have been developed to overcome the BBB in primary brain tumors. However, prognosis of most primary brain tumors still remains poor. The heterogeneity of the BBB in primary brain tumors and the distinct vasculature of tumors make it difficult to design a drug delivery method that targets the entire tumor. Drug delivery methods that combine strategies such as focused ultrasound and nanoparticles might be a more successful approach. However, more research is needed to optimize and develop new drug delivery techniques to improve survival of patients with primary brain tumors.

Purpose: The current standard-of-care for front-line therapy for acute myeloid leukaemia (AML) results in short-term and long-term toxicity, but still approximately 40% of children relapse. Therefore, there is a major need to accelerate the evaluation of innovative medicines, yet drug development continues to be adult-focused. Furthermore, the large number of competing agents in rare patient populations requires coordinated prioritisation, within the global regulatory framework and cooperative group initiatives. Methods: The fourth multi-stakeholder Paediatric Strategy Forum focused on AML in children and adolescents. Results: CD123 is a high priority target and the paediatric development should be accelerated as a proof-of-concept. Efforts must be coordinated, however, as there are a limited number of studies that can be delivered. Studies of FLT3 inhibitors in agreed paediatric investigation plans present challenges to be completed because they require enrolment of a larger number of patients than actually exist. A consensus was developed by industry and academia of optimised clinical trials. For AML with rare mutations that are more frequent in adolescents than in children, adult trials should enrol adolescents and when scientifically justified, efficacy data could be extrapolated. Methodologies and definitions of minimal residual disease need to be standardised internationally and validated as a new response criterion. Industry supported, academic sponsored platform trials could identify products to be further developed. The Leukaemia and Lymphoma Society PedAL/EUpAL initiative has the potential to be a major advance in the field. Conclusion: These initiatives continue to accelerate drug development for children with AML and ultimately improve clinical outcomes.

Purpose: Diffuse intrinsic pontine glioma (DIPG) is an incurable type of pediatric brain cancer, which in the majority of cases is driven by mutations in genes encoding histone 3 (H3K27M). We here determined the preclinical therapeutic potential of combined AXL and HDAC inhibition in these tumors to reverse their mesenchymal, therapy-resistant, phenotype. Experimental Design: We used public databases and patient-derived DIPG cells to identify putative drivers of the mesenchymal transition in these tumors. Patient-derived neurospheres, xenografts, and allografts were used to determine the therapeutic potential of combined AXL/HDAC inhibition for the treatment of DIPG. Results: We identified AXL as a therapeutic target and regulator of the mesenchymal transition in DIPG. Combined AXL and HDAC inhibition had a synergistic and selective antitumor effect on H3K27M DIPG cells. Treatment of DIPG cells with the AXL inhibitor BGB324 and the HDAC inhibitor panobinostat resulted in a decreased expression of mesenchymal and stem cell genes. Moreover, this combination treatment decreased expression of DNA damage repair genes in DIPG cells, strongly sensitizing them to radiation. Pharmacokinetic studies showed that BGB324, like panobinostat, crosses the blood–brain barrier. Consequently, treatment of patient-derived DIPG xenograft and murine DIPG allograft-bearing mice with BGB324 and panobinostat resulted in a synergistic antitumor effect and prolonged survival. Conclusions: Combined inhibition of AXL and HDACs in DIPG cells results in a synergistic antitumor effect by reversing their mesenchymal, stem cell-like, therapy-resistant phenotype. As such, this treatment combination may serve as part of a future multimodal therapeutic strategy for DIPG.

Purpose Proxy reports of health-related quality of life (HRQoL) are commonly used in pediatric oncology. However, it is not known if caregivers’ reports differ. This study therefore aims to compare paternal and maternal proxy reports, and explore determinants of couple disagreement (sociodemographic and medical characteristics, and parental QoL and distress). Methods Both parents completed the PedsQL generic (child’s HRQoL), Short Form-12 (own QoL) and Distress Thermometer for Parents. To assess agreement in child HRQoL, intra-class correlation coefficients (ICCs) were calculated. Differences between fathers/mothers were assessed with paired t tests. Systematic disagreement patterns were visualized with Bland–Altman plots. Characteristics of parental couples with a mean proxy difference in the highest quartile (highest proxy score minus lowest proxy score) were explored with multiple logistic regression analysis. Results Parents of 120 children with cancer (87% post-treatment, mean age 11.0 ± 5.7 years) participated. No significant differences were found between paternal and maternal proxy scores, and agreement was good on all scales (ICCs 0.65–0.83). Bland–Altman plots revealed no systematic disagreement patterns, but there was a wide range in magnitude of the differences, and differences went in both directions. Couples with a mean proxy difference (irrespective of which direction) in the highest quartile (± 20 points) were more likely to have a child in active treatment, with retinoblastoma or relapsed disease, and to diverge in their own QoL. Conclusions If proxy reports of only one parent are available, clinicians may reasonably assume that paternal and maternal reports are interchangeable. However, if in doubt, respondent’s sex is not of major importance, but clinicians should be aware of patient’s and family’s characteristics.