Risk of childhood neoplasms related to neonatal phototherapy- a systematic review and meta-analysis

CONTEXT

Observational studies have shown conflicting results as to whether exposure to neonatal phototherapy is associated with increased rates of childhood cancer.

OBJECTIVE

To describe the rates of childhood neoplasms and cancer after neonatal phototherapy.

DATA SOURCES

The CENTRAL, PubMed, Scopus, and Web of Science databases.

STUDY SELECTION

Observational studies regardless of design were included.

DATA EXTRACTION

The data were extracted by one author and validated by another. The risk-of-bias assessment was performed using the ROBINS-E and Joanna Briggs Institute critical appraisal tools.

RESULTS

Six cohort and 10 case-control studies were included. The overall risk of bias was high in seven and low in nine studies. In cohort studies, the odds ratio (OR) was increased for hematopoietic cancer (1.44; confidence interval [CI]: 1.16-1.80) and solid tumors (OR: 1.18; CI: 1.00-1.40). In case-control studies, the OR was 1.63 (CI: 0.99-2.67) for hematopoietic cancers and 1.18 (CI: 1.04-1.34) for solid tumors.

CONCLUSIONS

Children with a history of neonatal phototherapy had increased risk of hematopoietic cancer and solid tumors. The evidence quality was limited due to the high risk of bias and potential residual confounding.

IMPACT STATEMENT

Exposure to neonatal phototherapy increased later risk of hematopoietic cancer and solid tumors. This is the most comprehensive study on the association between phototherapy and cancer, but the evidence quality was limited due risk of bias and residual confounding. Future large scale well conducted studies are still needed to better estimate the association and.

Dual direction associations between common autoimmune diseases and leukemia among children and young adults: A systematic review

BACKGROUND

Childhood leukemia and many autoimmune (AI) diseases are severe pediatric conditions with lifelong consequences. AI diseases form a heterogeneous disease group affecting about 5 % of children worldwide, while leukemia is the most common malignancy among children aged 0-14 years. The timing and similarities in suggested inflammatory and infectious triggers of AI disease and leukemia have raised a question whether the diseases share common etiological origins. We conducted a systematic review to evaluate the evidence linking childhood leukemia and AI diseases.

DATA SOURCES

In the systematic literature search CINAHL (from 1970), Cochrane Library (form 1981), PubMed (from 1926) and Scopus (from 1948) were queried in June 2023.

REVIEW METHODS

We included studies covering the association between any AI disease and acute leukemia, limiting it to children and adolescents under 25 years old. The studies were reviewed independently by two researchers and the risk of bias was assessed.

RESULTS

A total of 2119 articles were screened and 253 studies were selected for detailed evaluation. Nine studies met the inclusion criteria, of which eight were cohort studies and one was a systematic review. The diseases covered were type 1 diabetes mellitus, inflammatory bowel diseases and juvenile arthritis alongside acute leukemia. Five cohort studies were suitable for more detailed analysis: a rate ratio for leukemia diagnosis after any AI disease was 2.46 (95 % CI 1.17-5.18; heterogeneity I2 15 %) with a random-effects model.

CONCLUSIONS

The results of this systematic review indicate that AI diseases in childhood are associated with a moderately increased risk of leukemia. The association for individual AI diseases needs further investigation.

Residential mobility and childhood inflammatory bowel disease: a nationwide case-control study

PURPOSE

To examine the association of residential mobility, as a proxy for environmental influences, with childhood inflammatory bowel disease (IBD) risk.

METHODS

Using nationwide register-based dataset, all 2038 IBD cases in Finland diagnosed at ages less than 15 years in 1992-2016 were individually matched by sex and age with five controls employing risk set sampling. Complete residential histories of the subjects were constructed from birth until the index date (diagnosis date of the case). Movement patterns were assessed by age, distance, and demographics of the departure and destination municipalities. Conditional logistic regression was employed to estimate the association between movements and IBD risk.

RESULTS

Overall, residential movement was associated with a slightly decreased odds ratio (OR) for childhood IBD (OR 0.97, 95% confidence interval (CI) 0.95-1.00 for each movement). Further examination showed reduced ORs for moving to rural municipalities (OR 0.94, 95% CI 0.90-0.98) and to distances less than 50 km (OR 0.96, 95% CI 0.93-0.99). In disease subtype analyses, the effect mainly persisted in ulcerative colitis.

CONCLUSIONS

Our findings suggest lower childhood IBD risk associated with residential mobility. The effect was found in ulcerative colitis, but not in Crohn's disease. Movements to nearby and rural areas may reduce IBD risk, though this requires further investigation.

Long-term mortality in pediatric solid organ recipients-A nationwide study

BACKGROUND

The present study aimed at investigating long-term mortality of patients who underwent solid organ transplantation during childhood and at identifying their causes of death.

METHODS

A cohort of 233 pediatric solid organ transplant recipients who had a kidney, liver, or heart transplantation between 1982 and 2015 in Finland were studied. Year of birth-, sex-, and hometown-matched controls (n = 1157) were identified using the Population Register Center registry. The Causes of Death Registry was utilized to identify the causes of death.

RESULTS

Among the transplant recipients, there were 60 (25.8%) deaths (median follow-up 18.0 years, interquartile range of 11.0-23.0 years). Transplant recipients' risk of death was nearly 130-fold higher than that of the controls (95% CI 51.9-1784.6). The 20-year survival rates for kidney, liver, and heart recipients were 86.1% (95% CI 79.9%-92.3%), 58.5% (95% CI 46.2%-74.1%), and 61.4% (95% CI 48.1%-78.4%), respectively. The most common causes of death were cardiovascular diseases (23%), infections (22%), and malignancies (17%). There were no significant differences in survival based on sex or transplantation era.

CONCLUSION

The late mortality is still significantly higher among pediatric solid organ recipients in comparison with controls. Cardiovascular complications, infections, and cancers are the main causes of late mortality for all studied transplant groups. These findings emphasize the cruciality of careful monitoring of pediatric transplant recipients in order to reduce long-term mortality.

Clustering of pediatric onset inflammatory bowel disease in Finland: a nationwide register-based study

BACKGROUND

The incidence of pediatric inflammatory bowel disease (PIBD) has increased dramatically during the past decades. This implies involvement of environmental factors in etiology but lends no clues about specific agents. We evaluated clustering in time and place of residence at PIBD onset using a case-control setting with comprehensive nationwide register data.

METHODS

We included all PIBD cases diagnosed at ages < 18 years during 1992-2017 (3748 cases; median age of 14.6; 2316 (58%) with ulcerative colitis (UC), 1432 with Crohn's, and 18,740 age- and sex-matched controls) and constructed complete residential histories (including coordinates) from the national database until the date of the diagnosis of the case assigned as index date for the controls. Using the coordinates of the addresses of the subjects and the diagnosis/index dates, we evaluated clustering in time and place using the Knox test. Four temporal (2, 4, 6, 12 months) and four distance (0.25, 0.5, 1, 5 km) thresholds were used, and results were calculated separately for Crohn´s disease and UC. Similar analyses were conducted using the addresses at birth and the addresses five years before the diagnosis or index date. Based on the threshold values displaying the most clustering in the Knox test, logistic regression models were built to identify whether sex, age at diagnosis or the year of diagnosis affected the probability of belonging to a cluster. To analyze clustering in time and place throughout the residential histories, we used Jacquez's Q with an open-access python program pyjacqQ.

RESULTS

The mean number of residencies until the index date was 2.91 for cases and 3.05 for controls (p = 0.0003). Knox test indicated residential clustering for UC with thresholds of 500 m between locations and time-period of four months (p = 0.004). In the regression analysis, sex, age at diagnosis or year of UC diagnosis did not show differences between the clustered and other cases. Jacquez Q analyses showed higher than expected frequency of clustered cases throughout residential histories (p < 10^- 8).

CONCLUSION

Our findings suggest that the incidence of PIBD, especially of UC, exhibits clustering in locations of residencies over time. For the clustered cases, environmental triggers warrant future studies.

Incidence trends of childhood central nervous system tumors in Finland 1990-2017

Introduction

Central nervous system (CNS) tumors are a leading cause of cancer-related morbidity and mortality in children. Our aim is to characterize incidence trends of pediatric CNS tumors in Finland over the last three decades.

Methods

Data on all benign and malignant incident CNS tumors diagnosed in children aged 0–14 years in 1990–2017 were extracted from the Finnish Cancer Registry and classified according to the 2016 WHO classification of CNS tumors. We analyzed age-standardized incidence rates (ASR) for pediatric CNS tumors overall and by sex, age, tumor histology, grade, and location using Poisson regression. We used joinpoint regression to evaluate changes in trends.

Results

Overall, 1117 pediatric CNS tumor cases were registered in Finland with a 1.2:1 male to female ratio. The average annual ASR was 4.3 per 100,000 person-years (95% CI 4.26, 4.34). The most common tumor type was pilocytic astrocytoma (30% of tumors), followed by medulloblastoma (10%) with incidence rates of 1.30 and 0.45 per 100,000 person-years, respectively. The overall incidence of pediatric CNS tumors increased by an annual percentage change (APC) of 0.8% (95% CI 0.2, 1.4). We observed no major changes in incidence trends of tumor histology groups or tumor location groups. The ASR of benign tumors increased by an APC of 1.0 (95% CI 0.1, 2.0).

Conclusions

Utilizing the high-quality and completeness of data in the Finnish Cancer registry, we found that the incidence of pediatric CNS tumors in Finland has increased slightly from 1990 until 2017. Although variations in diagnostic and registration practices over time might have affected the rates, the trend may also reflect a true increase in incidence.

Trends in ferritin measurements in children and adolescents: A Finnish 9-year observational study

Aim

A lack of stored iron, indicated by low serum ferritin, has been associated with various clinical symptoms. There are no longitudinal data on the frequency of ferritin measurements in children and adolescents.

Methods

A total of 2834 children aged <18 years with serum ferritin and other anaemia‐related blood parameters taken during an outpatient visit between 2012 and 2019 were investigated. Patients with acute infections were excluded. Nationwide temporal and regional variations and correlations with public information searches through Google were analysed.

Results

A significant increase in the frequency of ferritin measurements was seen starting in 2018, with a 47‐fold rise in 2019 compared to 2012. A simultaneous escalation in Google Search activity was seen. Deficiency of stored iron was relatively common: 21.6% of children with normal haemoglobin and 14.9% of non‐anaemic children with normal red cell indices exhibited ferritin levels below 15 μg/L.

Conclusion

Ferritin measurement has increased greatly among children and adolescents. Our results suggest that public interest and popular trends can significantly influence health care practices. This calls for further investigation into the causes and consequences of such a phenomenon. Prospective randomised intervention studies are needed to evaluate the utility of iron supplementation in patients with low iron storage levels.

Arginine Methyltransferase PRMT7 Deregulates Expression of RUNX1 Target Genes in T-Cell Acute Lymphoblastic Leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy with no well-established prognostic biomarkers. We examined the expression of protein arginine methyltransferases across hematological malignancies and discovered high levels of PRMT7 mRNA in T-ALL, particularly in the mature subtypes of T-ALL. The genetic deletion of PRMT7 by CRISPR-Cas9 reduced the colony formation of T-ALL cells and changed arginine monomethylation patterns in protein complexes associated with the RNA and DNA processing and the T-ALL pathogenesis. Among them was RUNX1, whose target gene expression was consequently deregulated. These results suggest that PRMT7 plays an active role in the pathogenesis of T-ALL.

Late adverse effects of childhood acute lymphoblastic leukemia treatment on developing dentition

BACKGROUND

Childhood cancer survivors show a variety of late adverse effects on dental health. The purpose of this study was to examine the prevalence and severity of dental abnormalities in permanent dentition in childhood leukemia survivors.

MATERIALS AND METHODS

Retrospective analysis of panoramic radiographs was performed for 178 childhood leukemia survivors aged below 17 years at the time of diagnosis. Sex, age at diagnosis, interval between ALL diagnosis and the follow-up radiograph, treatment protocol, and risk grouping were recorded. Abnormalities of tooth development and defect index were used to assess the frequency and severity of dental abnormalities.

RESULTS

One hundred eight (61%) patients had no dental abnormalities at follow-up examination at a median of 6.1 years after diagnosis. Microdontia was more frequent in children under 6 years of age at the time of diagnosis (5.7% vs. 0.6%, p < .001). Significant differences were noted between distinct ALL treatment protocols with more common microdontia in patients treated according to the NOPHO ALL2008 protocol. Tooth agenesis was more frequent in patients that underwent therapy according to high-risk arms compared to intermediate- or standard-risk arms (3.8% vs. 1.4%, p = .01). Patients under 6 years of age at diagnosis had a significantly higher average defect index score than older patients (7.0 vs. 2.8, p = .01).

CONCLUSIONS

Children and adolescents who received ALL treatment were at risk for dental damage. Young age and high-intensity therapy were associated with the severity of dental abnormalities.

Expression of BCL6 in paediatric B-cell acute lymphoblastic leukaemia and association with prognosis

B-cell lineage acute lymphoblastic leukaemia (B-ALL) is the most common paediatric malignancy. Transcription factor B-cell lymphoma 6 (BCL6) is essential to germinal centre formation and antibody affinity maturation and plays a major role in mature B-cell malignancies. More recently, it was shown to act as a critical downstream regulator in pre-BCR+ B-ALL. We investigated the expression of the BCL6 protein in a population-based cohort of paediatric B-ALL cases and detected moderate to strong positivity through immunohistochemistry in 7% of cases (8/117); however, only two of eight BCL6 cases (25%) co-expressed the ZAP70 protein. In light of these data, the subtype with active pre-BCR signalling constitutes a rare entity in paediatric B-ALL. In three independent larger cohorts with gene expression data, high BCL6 mRNA levels were associated with the TCF3-PBX1, Ph-like, NUTM1, MEF2D and PAX5-alt subgroups and the 'metagene' signature for pre-BCR-associated genes. However, higher-than-median BCL6 mRNA level alone was associated with favourable event free survival in the Nordic paediatric cohort, indicating that using BCL6 as a diagnostic marker requires careful design, and evaluation of protein level is needed alongside the genetic or transcriptomic data.

IGF2BP3 Associates with Proliferative Phenotype and Prognostic Features in B-Cell Acute Lymphoblastic Leukemia

The oncofetal protein insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) belongs to a family of RNA-binding proteins involved in localization, stability, and translational regulation of target RNAs. IGF2BP3 is used as a diagnostic and prognostic marker in several malignancies. Although the prognosis of pediatric B-cell acute lymphoblastic leukemia (B-ALL) has improved, a subgroup of patients exhibits high-risk features and suffer from disease recurrence. We sought to identify additional biomarkers to improve diagnostics, and we assessed expression of IGF2BP3 in a population-based pediatric cohort of B-ALL using a tissue microarray platform. The majority of pediatric B-ALL cases were positive for IGF2BP3 immunohistochemistry and were associated with an increased proliferative phenotype and activated STAT5 signaling pathway. Two large gene expression data sets were probed for the expression of IGF2BP3-the highest levels were seen among the B-cell lymphomas of a germinal center origin and well-established (KMT2A-rearranged and ETV6-RUNX1) and novel subtypes of B-ALL (e.g., NUTM1 and ETV6-RUNX1-like). A high mRNA for IGF2BP3 was associated with a proliferative "metagene" signature and a high expression of CDK6 in B-ALL. A low expression portended inferior survival in a high-risk cohort of pediatric B-ALL. Overall, our results show that IGF2BP3 shows subtype-specificity in expression and provides prognostic utility in high-risk B-ALL.

Randomized controlled and double-blinded study of Caphosol versus saline oral rinses in pediatric patients with cancer

BACKGROUND

Oral mucositis (OM) is a significant side effect of cancer treatment. The purpose of this study was to compare topically administered Caphosol to saline rinses in the prevention of mucositis in pediatric cancer patients.

PROCEDURE

A controlled, double-blinded, and randomized clinical crossover study recruited patients between 2 to 17.99 years of age who were diagnosed with a malignancy and were receiving either high-dose methotrexate (≥1 g/m² ), anthracycline, or cisplatin chemotherapy (NCT0280733). All patients received two 7-day cycles of the mouth rinses; that is, one cycle of Caphosol and one cycle of saline in a randomized order. Oral changes and symptoms were evaluated using the World Health Organisation (WHO) toxicity scale and the Children's International Mucositis Evaluation Scale (ChIMES). The primary endpoint was the frequency and severity of OM and oral symptoms.

RESULTS

A total of 56 patients were recruited to the study, of whom 45 were randomized with a median age of 6.5 years (range 2.1-17.1 years). No cases of severe OM were observed. Grade ≥ 3 oral symptoms were present at least once in six (13%) patients during the Caphosol cycle and 13 (29%) patients during the saline cycle (P = .12). The peak of symptom scores was evident at around day 4-7 after administration of the chemotherapy with no marked differences between the rinse solutions. Multivariable regression analysis did not indicate a benefit of using Caphosol over the saline solution.

CONCLUSIONS

No difference in prevention of oral mucositis was observed between the use of Caphosol or saline rinses.

SIX6 is a TAL1-regulated transcription factor in T-ALL and associated with inferior outcome

T-cell acute lymphoblastic leukemia (T-ALL) is a hematological malignancy driven by abnormal activity of transcription factors. Here we report an aberrant expression of the developmental transcription factor SIX6 in the TAL1-subtype of T-ALL. Our results demonstrate that the binding of TAL1 and GATA3 transcription factors into an upstream enhancer element directly regulates SIX6 expression. High expression of SIX6 was associated with inferior event-free survival within three independent patient cohorts. At a functional level, CRISPR-Cas9-mediated knockout of the SIX6 gene in TAL1 positive Jurkat cells induced changes in genes associated with the mTOR-, K-RAS-, and TNFα-related molecular signatures but did not impair cell proliferation or viability. There was also no acceleration of T-ALL development within a Myc driven zebrafish tumor model in vivo. Taken together, our results show that SIX6 belongs to the TAL1 regulatory gene network in T-ALL but is alone insufficient to influence the development or maintenance of T-ALL.

Abstract 3588: SIX6 is a TAL1-regulated transcription factor in T-cell acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most common type of cancer in pediatric patients. In these patients, 10-12% of leukemias are of T-cell lineage (T-ALL), but the incidence increases by age and is two to three times higher among adolescents and adults. T-ALL patients have done worse than B-ALL historically, but in the last decade they have obtained rather similar event-free survival rates at primary therapy, but at relapse the prognosis is poor. T-ALL can be subdivided into separate groups based on the expression of transcription factors such as TAL1, LMO1/2 and HOX family. However, this classification has not translated into more personalized treatments. Better knowledge would improve understanding of the development and maintenance of T-ALL and possibly lead to targeted therapies.

We recently compiled a large gene expression dataset that utilized a uniform platform (Affymetrix HG U133 Plus 2.0) across 36 hematological and lymphoid malignancies and healthy tissues (Mehtonen et al. 2019, Pölönen et al. 2019). This dataset includes 1,008 healthy samples and 4,418 leukemia samples of which 1,713 are acute myeloid leukemia, 1,304 precursor B-ALL, 801 chronic lymphocytic leukemia, 385 T-ALL, and 215 chronic myeloid leukemia. By utilizing this dataset, we searched for disease or subtype-specific transcriptional regulators and observed a high expression of SIX homeobox 6 (SIX6) gene in T-ALL. SIX6 is a transcription factor that normally functions in the retina of developing and adult eye, but only few studies have associated it with cancer.

Expression of SIX6 was highest in the TAL1 subgroup of T-ALL. Global nuclear Run-On sequencing (GRO-seq) of multiple T-ALL cell lines revealed an enhancer upstream of SIX6, whose activity correlated with expression of SIX6. Coinciding with this specific enhancer region, ChIP-seq analysis showed a binding of TAL1 and GATA3 transcription factors. Silencing of TAL1 and GATA3 expression significantly repressed expression of SIX6 (n = 4, p-value = 0.029, data from Sanda et al. 2012), thus lending further support of a direct regulation of SIX6 by TAL1. Co-expression of SIX6 together with the MYC oncogene in a Rag2:mMYC T-ALL zebrafish model did not affect leukemia progression. Clinical relevance of SIX6 gene expression was also studied in a patient cohort from TARGET dataset (n = 261), and a high expression of SIX6 was associated with an unfavorable trend in overall survival among T-ALL patients (p-value = 0.12).

In conclusion, SIX6 is a T-ALL-related transcription factor which is regulated by TAL1 and GATA3 transcription factors, and associates with less favorable prognosis, thus warranting further mechanistic studies in leukemia.

References:

Mehtonen et al. Nucleic Acids Res. 2019:26;47(13)

Pölönen et al. Cancer Res. 2019:15;79(10)

Sanda et al. Cancer Cell. 2012:22(2):209-21

Citation Format: Saara Laukkanen, Laura Oksa, Atte Nikkilä, Juha Mehtonen, Petri Pölönen, Mari Lahnalampi, Merja Heinäniemi, Olli Lohi. SIX6 is a TAL1-regulated transcription factor in T-cell acute lymphoblastic leukemia [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3588.

Epidemiological studies of natural sources of radiation and childhood cancer: current challenges and future perspectives

The empirical estimation of cancer risks in children associated with low-dose ionising radiation (<100 mSv) remains a challenge. The main reason is that the required combination of large sample sizes with accurate and comprehensive exposure assessment is difficult to achieve. An international scientific workshop, 'Childhood cancer and background radiation', organised by the Institute of Social and Preventive Medicine of the University of Bern, brought together researchers in this field to evaluate how epidemiological studies of background radiation and childhood cancer can best improve our understanding of the effects of low-dose ionising radiation. This review summarises and evaluates the findings of these studies with regard to their methodological differences, identifies key limitations and challenges, and proposes ways to move forward. Large childhood cancer registries, such as those in Great Britain, France and Germany, now permit the conducting of studies that should have sufficient statistical power to detect the effects predicted by standard risk models. Nevertheless, larger studies or pooled studies will be needed to investigate disease subgroups. The main challenge is to accurately assess children's individual exposure to radiation from natural sources and from other sources, as well as potentially confounding non-radiation exposures, in such large study populations. For this, the study groups should learn from each other to improve exposure estimation and develop new ways to validate exposure models with personal dosimetry.

Clinicopathological features and prognostic value of SOX11 in childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia is marked by aberrant transcriptional features that alter cell differentiation, self-renewal, and proliferative features. We sought to identify the transcription factors exhibiting altered and subtype-specific expression patterns in B-ALL and report here that SOX11, a developmental and neuronal transcription factor, is aberrantly expressed in the ETV6-RUNX1 and TCF3-PBX1 subtypes of acute B-cell leukemias. We show that a high expression of SOX11 leads to alterations of gene expression that are typically associated with cell adhesion, migration, and differentiation. A high expression is associated with DNA hypomethylation at the SOX11 locus and a favorable outcome. The results indicate that SOX11 expression marks a group of patients with good outcomes and thereby prompts further study of its use as a biomarker.

Cancer morbidity and mortality after pediatric solid organ transplantation-a nationwide register study

BACKGROUND

The prevalence of malignancies after pediatric solid organ transplantation was evaluated in a nationwide study.

METHODS

All patients who had undergone kidney, liver, or heart transplantation during childhood between the years 1982 and 2015 in Finland were identified. The inclusion criteria were age under 16 years at transplantation and age over 18 years at the last follow-up day. A total of 233 (137 kidney, 53 liver, and 43 heart) transplant recipients were enrolled. Controls (n = 1157) matched by the year of birth, gender, and hometown were identified using the Population Register Center registry. The cancer diagnoses were searched using the Finnish Cancer Registry.

RESULTS

Altogether 26 individuals diagnosed with cancer were found, including 18 transplant recipients. Cancer was diagnosed at a median of 12.0 (IQR 7.8-17.8) years after the transplantation. The transplant recipients' risk for cancer was significantly higher when compared with the controls (HR 14.7; 95% CI 6.4-33.9). There was no difference for different graft types. Sixty-one percent of cancers among the transplant recipients were diagnosed at age older than 18 years.

CONCLUSION

The risk for cancer is significantly higher among young adults having undergone solid organ transplantation during childhood in comparison with population controls. Careful follow-up and attention to prevent cancers throughout adulthood are warranted.

Parental occupational exposure to low-frequency magnetic fields and risk of leukaemia in the offspring: findings from the Childhood Leukaemia International Consortium (CLIC)

OBJECTIVES

Previously published studies on parental occupational exposure to extremely low-frequency magnetic fields (ELF-MF) and risk of acute lymphoblastic leukaemia (ALL) and acute myeloid leukaemia (AML) in their offspring were inconsistent. We therefore evaluated this question within the Childhood Leukemia International Consortium.

METHODS

We pooled 11 case-control studies including 9723 childhood leukaemia cases and 17 099 controls. Parental occupational ELF-MF exposure was estimated by linking jobs to an ELF-MF job-exposure matrix (JEM). Logistic regression models were used to estimate ORs and 95% CIs in pooled analyses and meta-analyses.

RESULTS

ORs from pooled analyses for paternal ELF-MF exposure >0.2 microtesla (µT) at conception were 1.04 (95% CI 0.95 to 1.13) for ALL and 1.06 (95% CI 0.87 to 1.29) for AML, compared with ≤0.2 µT. Corresponding ORs for maternal ELF-MF exposure during pregnancy were 1.00 (95% CI 0.89 to 1.12) for ALL and 0.85 (95% CI 0.61 to 1.16) for AML. No trends of increasing ORs with increasing exposure level were evident. Furthermore, no associations were observed in the meta-analyses.

CONCLUSIONS

In this large international dataset applying a comprehensive quantitative JEM, we did not find any associations between parental occupational ELF-MF exposure and childhood leukaemia.

Effects of incomplete residential histories on studies of environmental exposure with application to childhood leukaemia and background radiation

When evaluating environmental exposures, residential exposures are often most relevant. In most countries, it is impossible to establish full residential histories. In recent publications, childhood leukaemia and background radiation have been studied with and without full residential histories. This paper investigates the consequences of lacking such full data. Data from a nationwide Finnish Case-Control study of Childhood Leukaemia and gamma rays were analysed. This included 1093 children diagnosed with leukaemia in Finland in 1990-2011. Each case was matched by gender and year of birth to three controls. Full residential histories were available. The dose estimates were based on outdoor background radiation measurements. The indoor dose rates were obtained with a dwelling type specific conversion coefficient and the individual time-weighted mean red bone marrow dose rates were calculated using age-specific indoor occupancy and the age and gender of the child. Radiation from Chernobyl fallout was included and a 2-year latency period assumed. The median separation between successive dwellings was 3.4 km and median difference in red bone marrow dose 2.9 nSv/h. The Pearson correlation between the indoor red bone marrow dose rates of successive dwellings was 0.62 (95% CI 0.60, 0.64). The odds ratio for a 10 nSv/h increase in dose rate with full residential histories was 1.01 (95% CI 0.97, 1.05). Similar odds ratios were calculated with dose rates based on only the first dwelling (1.02, 95% CI 0.99, 1.05) and only the last dwelling (1.00, 95% CI 0.98, 1.03) and for subjects who had lived only in a single dwelling (1.05, 95% CI 0.98, 1.10). Knowledge of full residential histories would always be the option of choice. However, due to the strong correlation between exposure estimates in successive dwellings and the uncertainty about the most relevant exposure period, estimation of overall exposure level from a single address is also informative. Error in dose estimation is likely to cause some degree of classical measurement error resulting in bias towards the null.

Radiation exposure from computerized tomography and risk of childhood leukemia: Finnish register-based case-control study of childhood leukemia (FRECCLE)

The only well-established risk factors for childhood leukemia are high-dose ionizing radiation and Down syndrome. Computerized tomography is a common source of low-dose radiation. In this study, we examined the magnitude of the risk of childhood leukemia after pediatric computed tomography examinations. We evaluated the association of computed tomography scans with risk of childhood leukemia in a nationwide register-based case-control study. Cases (n=1,093) were identified from the population-based Finnish Cancer Registry and three controls, matched by gender and age, were randomly selected for each case from the Population Registry. Information was also obtained on birth weight, maternal smoking, parental socioeconomic status and background gamma radiation. Data on computed tomography scans were collected from the ten largest hospitals in Finland, covering approximately 87% of all pediatric computed tomography scans. Red bone marrow doses were estimated with NCICT dose calculation software. The data were analyzed using exact conditional logistic regression analysis. A total of 15 cases (1.4%) and ten controls (0.3%) had undergone one or more computed tomography scans, excluding a 2-year latency period. For one or more computed tomography scans, we observed an odds ratio of 2.82 (95% confidence interval: 1.05 – 7.56). Cumulative red bone marrow dose from computed tomography scans showed an excess odds ratio of 0.13 (95% confidence interval: 0.02 – 0.26) per mGy. Our results are consistent with the notion that even low doses of ionizing radiation observably increase the risk of childhood leukemia. However, the observed risk estimates are somewhat higher than those in earlier studies, probably due to random error, although unknown predisposing factors cannot be ruled out.

Fetal growth and congenital malformations

OBJECTIVES

To ascertain whether the risk for congenital malformations is increased in pregnancies with deviating fetal growth, i.e. in those in which the estimated date of delivery (EDD) was postponed more than 1 week at the second-trimester ultrasound fetometry scan, or those suspected of intrauterine growth restriction at routine ultrasound fetometry in the third trimester.

METHODS

The study period was 1994-2003. We used the Swedish Medical Birth Register to identify pregnancies with appropriate data (n = 605 845). A regional ultrasound database consisting of 73 092 pregnancies was used for more detailed data and analysis of the third-trimester fetal growth. The number of congenital malformations was ascertained from three national health registers.

RESULTS

We found a moderately increased risk for any malformation in the group of fetuses in which the EDD was postponed > 1 week. The strongest effect was seen for chromosome anomalies and central nervous system malformations, including neural tube defects. In the third trimester, an increased risk for fetal malformations was found in asymmetrically vs. symmetrically growth-restricted fetuses, perhaps more strongly when adjustment of the EDD had been done at the dating scan.

CONCLUSIONS

Fetuses in which the EDD differs between that calculated by the last menstrual period and that calculated by second-trimester ultrasound measurement seem to have an increased risk for congenital malformations, including chromosomal anomalies. A targeted ultrasound examination for malformation screening might be recommended for this group. A similar policy might be recommended when intrauterine growth restriction, especially of the asymmetrical type, is suspected later in pregnancy.

Bioaccumulation of PCBs in burbot (Lota lota L.) after delivery in natural food

Burbot (Lota lota) caught from Lake Päijänne, Central Finland, were exposed under laboratory conditions to four polychlorinated biphenyl (PCB) congeners delivered through diet, and accumulation of congeners to muscle, intestine, gonads, and liver were determined. The selected PCB congeners (PCB18, PCB44, PCB137, and PCB169) were added to intact dead vendace (Coregonus albula) and burbot were fed 5 or 10 contaminated meals (2- and 4-week experiment, respectively). Concentrations of fed congeners were different in the examined tissues. The highest concentrations of all the congeners were found in the livers of burbot. The mean retention efficiencies were 65.0% and 81.7% after 5 and 10 oral doses, respectively. The retention efficiency of the coplanar 169 was lower than those of the other fed congeners. The background organochlorine concentrations of the burbot of this study were compared with the PCB concentrations of burbot caught in the 1970s from Lake Päijänne. These concentrations were compared in order to clarify the PCB load and persistence in a boreal aquatic food web. The total PCB concentration in burbot has not declined during the last decades. The most abundant PCB congeners in the field were PCB138 and PCB153. Residual concentrations of pesticides were also found, especially the DDE, which is a metabolite of DDT.

How to identify twins at low risk of spontaneous preterm delivery

OBJECTIVE

The aim of this study was to evaluate transvaginal sonographic assessment of cervical length at 23 weeks as a screening test for spontaneous preterm delivery in order to define a cut-off value that could be used to select twin pregnancies at low risk of spontaneous preterm delivery.

METHODS

In a prospective multicenter study of 383 twin pregnancies included before 14 + 6 weeks a cervical scan with measurement of the cervical length was performed at 23 weeks' gestation. The results were blinded for the clinicians if the cervical length was > or = 15 mm. The rates of spontaneous delivery at different cut-off levels of cervical length were determined.

RESULTS

Eighty-nine percent of the twins had dichorionic placentation and 58% were conceived after assisted reproduction. The rate of spontaneous preterm delivery was 2.3% (1.5% for dichorionic (DC) and 9.1% for (MC) monochorionic twins) before 28 weeks and 18.5% (17.1% for DC and 29.5% for MC twins) before 35 weeks. The screen-positive rate was 5% for a cervical length < or = 20, 7-8% at < or = 25, 16-17% at < or = 30 and 34-48% at < or = 35 mm depending on chorionicity. The false-negative rate (1 - negative predictive value) ranged from 1.2% at 28 weeks to 18.6% at 35 weeks for all twins. Receiver-operating characteristics curves showed that the sensitivity increased with declining gestational age with cut-off levels of highest accuracy at 21 mm for 28 weeks and 29 mm for 33 weeks.

CONCLUSIONS

Cervical length measurement at 23 weeks of gestation is a good screening test for predicting twins at low risk of preterm and very preterm delivery, especially in DC twins. The present results suggest that a cut-off of 25 mm should be recommended.

Early amniocentesis and congenital foot deformities

OBJECTIVE

Several studies have shown an increased risk of congenital foot derformities after early amniocentesis. These studies have comprised amniocenteses performed before 13 completed gestational weeks. In this study, the risk of foot deformities after amniocentesis performed at 12-14 completed gestational weeks was determined.

METHODS

3,469 genetic amniocenteses in singleton pregnancies performed before 15 completed gestational weeks were studied. The intention was to perform the amniocenteses at 12-14 weeks of gestation, but 32 amniocenteses were performed at the gestational age 11 weeks + 5 days or 11 weeks + 6 days. The pregnancies were followed up with regard to fetal loss and leakage of amniotic fluid. After birth, newborns with a diagnosis of foot deformity were identified from the Swedish Medical Birth Registry. The observed number of foot deformities was then compared with the expected number which was calculated stratified for delivery hospital, year of birth, and maternal age.

RESULTS

The observed number of foot deformities was significantly higher than the expected: exact odds ratio 1.74 (exact 95% confidence interval 1.06-2.69). The rate of spontaneous abortions after the procedure was 1.8%, and the rate of leakage of amniotic fluid was 1.9%. There was a significant trend for all complications to decrease with increasing gestational age at amniocentesis.

CONCLUSION

Women undergoing amniocentesis at 11+5 to 14+6 gestational weeks have an increased risk of giving birth to a child with a congenital foot deformity.

Atrazine uptake, elimination, and bioconcentration by periphyton communities and Daphnia magna: effects of dissolved organic carbon

The bioconcentration and toxicokinetics of atrazine in three different periphyton communities and in laboratory reared Daphnia magna were studied in natural and artificial waters with different dissolved organic carbon (DOC) concentrations and qualities. The exposure concentrations were similar to those short-lived peak concentrations found in contaminated waters. Atrazine uptake and elimination were very fast, and the bioconcentration was low both in periphyton and D. magna. The bioconcentration factors in D. magna were approx. 16% of those in periphyton. The uptake and elimination rates were also higher in periphyton than in Daphnia. The periphyton properties affected the bioconcentration of atrazine more than the DOC concentration and water quality. A steady state was reached within a few hours of uptake by the periphyton and within 24 h by D. magna. A residue of atrazine was left in the periphyton and D. magna after an 8-h biphasic depuration with clearly distinct fast and slow phases. In D. magna, atrazine may be eliminated during the normal life span of the organism. These results suggest that DOC has a minor influence on the toxicokinetics of atrazine.

Effects of dissolved organic material on binding and toxicokinetics of pyrene in the waterflea Daphnia magna

The binding and bioavailability of pyrene was studied in the laboratory in two humic fresh waters and in a reference water without dissolved organic material (DOM), measured as dissolved organic carbon (DOC). The uptake of pyrene by Daphnia magna in short-term (24 h) accumulation experiments was fitted to a first-order rate-kinetic equation to calculate simultaneous uptake and elimination rates. The partition coefficients of pyrene to DOC (KDOC) were 37.1 x 103 in Pielisjoki River (9.4 mg DOC L(-1)), and 34.9 x 103 in Lake Kontiolampi (17.4 mg DOC L(-1)) waters, indicating similar binding affinities of pyrene for both humic waters. The uptake clearance of pyrene (ku) in the DOC-rich Lake Kontiolampi water was 290.4 ml g wet weight(-1) h(-1), which was lower than those in Pielisjoki River and DOC-free waters (395.8 and 346.0 ml g wet weight(-1) h(-1), respectively). Pyrene elimination (ke) was in average 0.2 h(-1) with no significant differences between the waters. The observed bioconcentration factors of pyrene in Pielisjoki River and Lake Kontiolampi waters were 84% and 46% of that in the DOC-free reference water, respectively, thus indicating that a high concentration of DOC is needed to decrease the bioavailability of waterborne pyrene to D. magna.

UV-B-Induced acute toxicity of pyrene to the waterflea Daphnia magna in natural freshwaters

The effects of various water characteristics in natural freshwaters on the acute toxicity of one polycyclic aromatic hydrocarbon (PAH), pyrene, to a pelagic invertebrate Daphnia magna was studied under ultraviolet B (UV-B) radiation and in the dark. Pyrene was photoactivated and was more toxic to D. magna in the presence of UV-B radiation. Dissolved organic material (DOM), measured as dissolved organic carbon (DOC), significantly reduced the photoenhanced toxicity of pyrene. Under UV-B radiation the EC(50) values were lower and in relation to the amount of DOM, ranging from 3.0 to 30.0 microg/L pyrene, whereas in the dark they were between 29.2 and 54.8 microg/L and not related to the amount of DOM in the waters. Although the condition and mortality of the daphnids in the control groups were not affected by UV-B irradiation, the increased toxicity was considered to be either an additive or a synergistic effect of both the photomodified pyrene and the stressing light conditions of UV-B. The measured binding of pyrene to DOM was low, although it was related to the amount of DOC. Despite the relatively high intensity of UV-B used, humic substances in the waters remained undegraded. It was thus concluded that with their brownish-yellowish color, waters rich in humic substances decreased the photomodification of the freely dissolved parent compound simply by diminishing the light penetration in these waters and, by implication, contact with the intact compound. These results suggest that DOM in surface waters plays an important role in protecting against the photoinduced toxicity of PAHs.

Metabolic and hormonal effects of exercise in mild streptozotocin diabetes

Metabolic and hormonal changes produced by muscular exercise were studied in rats with mild streptozotocin diabetes. In both diabetic and control animals the mean blood glucose increased and liver glycogen decreased during exercise. The postexercise blood glucose level correlated with the liver glycogen content in diabetic rats. A decrease of blood glucose occurred in some diabetic animals, and these also showed a decrease of liver glycogen to very low levels during exercise. During exercise the rise of plasma glycerol was higher in diabetic than in control animals, but changes in circulating free fatty acids, acetone bodies, insulin, corticosterone, lactate, and acid-base equilibrium were similar in the two groups. The results indicate that the only abnormal metabolic response to exercise in rats with mild diabetes is a slight increase of lipid mobilization.