Reduced occurrence of childhood cancer in twins compared to singletons: protection but by what mechanism?

Birth characteristics and childhood leukemia in Switzerland: a register-based case-control study

Purpose

Initial genetic alterations in the development of childhood leukemia occur in utero or before conception; both genetic and environmental factors are suspected to play a role. We aimed to investigate the associations between childhood leukemia and perinatal characteristics including birth order, birth interval to older siblings, parental age, birth weight, and multiple birth.

Methods

We identified cases diagnosed between 1981 and 2015 and born in Switzerland between 1969 and 2015 from the Swiss Childhood Cancer Registry and randomly sampled five controls per case from national birth records matched on date of birth, sex, and municipality of residence at birth. We used conditional logistic regression to investigate associations between perinatal characteristics and leukemia at ages 0–15 and 0–4 years, and the subtypes acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML).

Results

The study included 1,403 cases of leukemia. We observed increased risks associated with high birth weight (adjusted OR 1.37, 95% CI 1.12–1.69) and multiple birth (1.89, 1.24–2.86). These associations were similar for ALL and stronger for leukemia at ages 0–4 years. For AML, we observed an increased risk for higher birth order (3.08, 0.43–22.03 for fourth or later born children). We found no associations with other perinatal characteristics.

Conclusion

This register-based case–control study adds to the existing evidence of a positive association between high birth weight and risk of childhood leukemia. Furthermore, it suggests children from multiple births are at an increased risk of leukemia.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10552-021-01423-3.

A review of the types of childhood cancer associated with a medical X-ray examination of the pregnant mother

PURPOSE

For 65 years the interpretation of the statistical association between the risk of cancer in a child and a prior diagnostic X-ray examination of the abdomen of the pregnant mother has been debated. The objections to a direct cause-and-effect explanation of the association vary in their strength, but one of the most notable grounds for controversy is the finding from the first and largest case-control study reporting the association, the Oxford Survey of Childhood Cancers (OSCC), of an almost uniformly raised relative risk (RR) for nearly all of the types of cancer that are most frequent in children. Here we compare the antenatal X-ray associations found in the OSCC for different types of childhood cancer with the results of all other case-control and case-cohort studies appropriately combined in meta-analyses, and we also review the findings of the few cohort studies that have been conducted.

CONCLUSIONS

From the case-control/case-cohort studies other than the OSCC there are consistent and clear elevations of risk for all types of childhood cancer combined, all leukemia, and all cancers except leukemia combined. This compatibility of the findings of the OSCC with those of the combined other studies is less clear, or effectively absent, when some categories containing smaller numbers of incident cases/deaths are considered, but lack of precision of risk estimates due to sparse data presents inferential challenges, although there is a consistent absence of an association for bone tumors. Further, more recent studies almost certainly address lower intrauterine doses, with an anticipated decrease in estimated risks, which could be misleading when comparisons involve a limited number of studies that are mainly from later years, and a similar problem arises when having to employ all types of antenatal X-ray exposures for a study because data for abdominal exposures are absent. The problem of low statistical power is greater for cohort studies, and this, together with other shortcomings identified in the studies, limits the interpretational value of results. The findings of non-medical intrauterine exposure studies are constrained by sparse data and make a limited contribution to an understanding of the association. Certain aspects of the various studies require a need for caution in interpretation, but overall, the appropriate combination of all case-control/case-cohort studies other than the OSCC lends support to the inference that low-level exposure to radiation in utero proportionally increases the risk of the typical cancers of childhood to around the same level.

Compare and contrast: pediatric cancer versus adult malignancies

Cancer is a leading cause of death in both adults and children, but in terms of absolute numbers, pediatric cancer is a relatively rare disease. The rarity of pediatric cancer is consistent with our current understanding of how adult malignancies form, emphasizing the view of cancer as a genetic disease caused by the accumulation and selection of unrepaired mutations over time. However, considering those children who develop cancer merely as stochastically "unlucky" does not fully explain the underlying aetiology, which is distinct from that observed in adults. Here, we discuss the differences in cancer genetics, distribution, and microenvironment between adult and pediatric cancers and argue that pediatric tumours need to be seen as a distinct subset with their own distinct therapeutic challenges. While in adults, the benefit of any treatment should outweigh mostly short-term complications, potential long-term effects have a much stronger impact in children. In addition, clinical trials must cope with low participant numbers when evaluating novel treatment strategies, which need to address the specific requirements of children.

Childhood cancer research in Oxford II: The Childhood Cancer Research Group

BACKGROUND

We summarise the work of the Childhood Cancer Research Group, particularly in relation to the UK National Registry of Childhood Tumours (NRCT).

METHODS

The Group was responsible for setting up and maintaining the NRCT. This registry was based on notifications from regional cancer registries, specialist children's tumour registries, paediatric oncologists and clinical trials organisers. For a large sample of cases, data on controls matched by date and place of birth were also collected.

RESULTS

Significant achievements of the Group include: studies of aetiology and of genetic epidemiology; proposals for, and participation in, international comparative studies of these diseases and on a classification system specifically for childhood cancer; the initial development of, and major contributions to, follow-up studies of the health of long-term survivors; the enhancement of cancer registration records by the addition of clinical data and of birth records. The Group made substantial contributions to the UK government's Committee on Medical Aspects of Radiation in the Environment.

CONCLUSION

An important part of the ethos of the Group was to work in collaboration with many other organisations and individuals, both nationally and internationally: many of the Group's achievements described here were the result of such collaborations.

Infant birthweight and risk of childhood cancer: international population-based case control studies of 40 000 cases

BACKGROUND

High birthweight is an established risk factor for childhood leukaemia. Its association with other childhood cancers is less clear, with studies hampered by low case numbers.

METHODS

We used two large independent datasets to explore risk associations between birthweight and all subtypes of childhood cancer. Data for 16 554 cases and 53 716 controls were obtained by linkage of birth to cancer registration records across five US states, and 23 772 cases and 33 206 controls were obtained from the UK National Registry of Childhood Tumours. US, but not UK, data were adjusted for gestational age, birth order, plurality, and maternal age and race/ethnicity.

RESULTS

Risk associations were found between birthweight and several childhood cancers, with strikingly similar results between datasets. Total cancer risk increased linearly with each 0.5 kg increase in birthweight in both the US [odds ratio 1.06 (95% confidence interval 1.04, 1.08)] and UK [1.06 (1.05, 1.08)] datasets. Risk was strongest for leukaemia [USA: 1.10 (1.06, 1.13), UK: 1.07 (1.04, 1.10)], tumours of the central nervous system [USA: 1.05 (1.01, 1.08), UK: 1.07 (1.04, 1.10)], renal tumours [USA: 1.17 (1.10, 1.24), UK: 1.12 (1.06, 1.19)] and soft tissue sarcomas [USA: 1.12 (1.05, 1.20), UK: 1.07 (1.00, 1.13)]. In contrast, increasing birthweight decreased the risk of hepatic tumours [USA: 0.77 (0.69, 0.85), UK: 0.79 (0.71, 0.89) per 0.5 kg increase]. Associations were also observed between high birthweight and risk of neuroblastoma, lymphomas, germ cell tumours and malignant melanomas. For some cancer subtypes, risk associations with birthweight were non-linear. We observed no association between birthweight and risk of retinoblastoma or bone tumours.

CONCLUSIONS

Approximately half of all childhood cancers exhibit associations with birthweight. The apparent independence from other factors indicates the importance of intrauterine growth regulation in the aetiology of these diseases.

Cancer risk among children born after assisted conception

BACKGROUND

Accurate population-based data are needed on the incidence of cancer in children born after assisted conception.

METHODS

We linked data on all children born in Britain between 1992 and 2008 after assisted conception without donor involvement with data from the United Kingdom National Registry of Childhood Tumours to determine the number of children in whom cancer developed before 15 years of age. Cohort cancer rates were compared with population-based rates in Britain over the same period, with stratification for potential mediating and moderating factors, including sex, age at diagnosis, birth weight, singleton versus multiple birth, parity, parental age, type of assisted conception, and cause of parental infertility.

RESULTS

The cohort consisted of 106,013 children born after assisted conception (700,705 person-years of observation). The average duration of follow-up was 6.6 years. Overall, 108 cancers were identified, as compared with 109.7 expected cancers (standardized incidence ratio, 0.98; 95% confidence interval [CI], 0.81 to 1.19; P=0.87). Assisted conception was not associated with an increased risk of leukemia, neuroblastoma, retinoblastoma, central nervous system tumors, or renal or germ-cell tumors. It was associated with an increased risk of hepatoblastoma (standardized incidence ratio, 3.64; 95% CI, 1.34 to 7.93; P=0.02; absolute excess risk, 6.21 cases per 1 million person-years) and rhabdomyosarcoma (standardized incidence ratio, 2.62; 95% CI, 1.26 to 4.82; P=0.02; absolute excess risk, 8.82 cases per 1 million person-years), with hepatoblastoma developing in 6 children and rhabdomyosarcoma in 10 children. The excess risk of hepatoblastoma was associated with low birth weight.

CONCLUSIONS

There was no increase in the overall risk of cancer among British children born after assisted conception during the 17-year study period. Increased risks of hepatoblastoma and rhabdomyosarcoma were detected, but the absolute risks were small. (Funded by Cancer Research UK and others.).

Childhood and adult cancers: contrasts and commonalities

Tumours occurring in children differ considerably from those occurring at older ages but exhibit common features. Those occurring in the teenage/young adult (TYA) years represent a transitional mixture of child and adult tumours and pose a considerable challenge for optimal clinical management and service provision. Nevertheless the fundamental processes of malignant change, arising from genetic/epigenetic interaction with environmental exposures, seem to operate across all ages and the entire tumour spectrum. We focus here on the ways in which genotype (and epigenetic modification), growth processes (particularly in utero), and exposure to ionising radiation (in conjunction with genetic susceptibility) affect cancer risk from childhood to adulthood, whether as a primary occurrence, or a second primary tumour following earlier primary occurrence and treatment.

In vitro fertilization and risk of childhood leukemia in Greece and Sweden

BACKGROUND

Cancer risk in children born after in vitro fertilization (IVF) remains largely unknown. We aimed to investigate risk of leukemia and lymphoma following IVF using two nationwide datasets.

METHODS

The hospital-based case-control study in Greece derived from the National Registry for Childhood Hematological Malignancies (1996-2008, 814 leukemia and 277 lymphoma incident cases with their 1:1 matched controls). The Swedish case-control study was nested in the Swedish Medical Birth Register (MBR) (1995-2007, 520 leukemia and 71 lymphoma cases with their 5,200 and 710 matched controls) with ascertainment of incident cancer cases in the National Cancer Register. Study-specific and combined odds ratios (OR) were estimated using conditional logistic regression, with adjustment for possible risk factors.

RESULTS

Nationwide studies pointed to similar size excess risk of leukemia following IVF, but to a null association between IVF and lymphoma. The proportion of leukemia cases conceived through IVF was 3% in Greece and 2.7% in Sweden; prevalence of IVF in matched controls was 1.8% and 1.6%, respectively. In combined multivariable analyses, the increased risk of leukemia was confined to age below 3.8 years (OR = 2.21; 95% confidence interval, CI: 1.27-3.85) and to acute lymphoblastic leukemia (ALL) (OR = 1.77; 95% CI: 1.06-2.95) with no sufficient evidence of excess risk for other leukemias (OR = 1.34; 95% CI: 0.38-4.69). Following IVF, OR for ALL was 2.58 (95% CI: 1.37-4.84) before age 3.8 and 4.29 (95% CI: 1.49-12.37) before age 2 years.

CONCLUSIONS

IVF seems to be associated with increased risk of early onset ALL in the offspring.

Cancer risks associated with external radiation from diagnostic imaging procedures

The 600% increase in medical radiation exposure to the US population since 1980 has provided immense benefit, but increased potential future cancer risks to patients. Most of the increase is from diagnostic radiologic procedures. The objectives of this review are to summarize epidemiologic data on cancer risks associated with diagnostic procedures, describe how exposures from recent diagnostic procedures relate to radiation levels linked with cancer occurrence, and propose a framework of strategies to reduce radiation from diagnostic imaging in patients. We briefly review radiation dose definitions, mechanisms of radiation carcinogenesis, key epidemiologic studies of medical and other radiation sources and cancer risks, and dose trends from diagnostic procedures. We describe cancer risks from experimental studies, future projected risks from current imaging procedures, and the potential for higher risks in genetically susceptible populations. To reduce future projected cancers from diagnostic procedures, we advocate the widespread use of evidence-based appropriateness criteria for decisions about imaging procedures; oversight of equipment to deliver reliably the minimum radiation required to attain clinical objectives; development of electronic lifetime records of imaging procedures for patients and their physicians; and commitment by medical training programs, professional societies, and radiation protection organizations to educate all stakeholders in reducing radiation from diagnostic procedures.

Immunophenotype and cytogenetic characteristics in the relationship between birth weight and childhood leukemia

BACKGROUND

High birth weight increases the risk of childhood acute lymphoid leukemia (ALL) through unknown mechanisms. Whether this risk is specific to ALL subtypes is unknown, and low case numbers have prevented investigation of the rarer leukemias. Here we address these associations using a large population-based dataset.

PROCEDURE

Using the National Registry of Childhood Tumors, birth weights of 7,826 leukemia cases, defined by immunophenotype and cytogenetic subgroup, were compared with those of 10,785 controls born in England and Wales between 1980 and 2007.

RESULTS

The risk for overall leukemia increases 7% with each 0.5 kg increase in birth weight (OR 1.07, 95%CI 1.04-1.10). This risk is limited to the lymphoid leukemias (OR 1.08, 95%CI 1.05-1.12) diagnosed between 1 and 9 years of age. Analysis by cytogenetic feature reveals that there appears to be association with specific chromosomal abnormality: the risk of tumors with high hyperdiploid karyotypes increases 12% per 0.5 kg increase in birth weight (OR 1.12, 95%CI 1.05-1.20), and t(1;19) tumors show an increased risk of 41% per 0.5 kg increase (OR 1.41, 95%CI 1.09-1.84). The risk of acute myeloid leukemia is elevated in high and low birth weight babies. There is no significant risk relationship to other leukemias or myeloproliferative diseases.

CONCLUSIONS

Birth weight is a risk factor for ALL and AML. Other subtypes of the disease are not significantly affected. There appears to be association with specific chromosomal abnormality, which may aid our understanding of the development of childhood leukemia in utero.

Childhood cancer among twins and higher order multiples

Although several studies have found no change or a decreased risk of childhood cancer in twins, few have controlled for potential confounders such as birth weight. We examined the association of birth plurality and childhood cancer in pooled data from five U.S. states (California, Minnesota, New York, Texas, and Washington) using linked birth-cancer registry data. The data, excluding children with Down syndrome or who died before 28 days of life, included 17,672 cases diagnosed from 1980 to 2004 at ages 28 days to 14 years and 57,966 controls with all cases and controls born from 1970 to 2004. Analyses were restricted to children weighing Collapse

Key Words

• childhood cancer
• twins
• multiple birth
• case-control
• pooled data

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MESH Headings

• Adolescent
• Case-Control Studies
• Child
• Child, Preschool
• Diseases in Twins/epidemiology
• Female
• Humans
• Infant
• Infant, Newborn
• Kidney Neoplasms/epidemiology
• Logistic Models
• Male
• Multiple Birth Offspring
• Neoplasms/epidemiology
• Registries
• Retinal Neoplasms/epidemiology
• Retinoblastoma/epidemiology
• Risk Factors
• United States/epidemiology
• Wilms Tumor/epidemiology

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Grants

• R01CA717450 NCI NIH HHS
• R01 CA092670-04 NCI NIH HHS
• U58 DP000783 NCCDPHP CDC HHS
• R01CA92670 NCI NIH HHS
• R01 CA092670 NCI NIH HHS
• T32 CA099936-04 NCI NIH HHS
• N01 CN005230 NCI NIH HHS
• R01 CA071745-04 NCI NIH HHS
• T32 CA099936 NCI NIH HHS

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Affiliation(s)

Susan E. Puumala Division of Epidemiology/Clinical Research, Department of Pediatrics, University of Minnesota
Susan E. Carozza Department of Epidemiology and Biostatistics, Texas A&M University
Eric J. Chow Fred Hutchinson Cancer Research Center
Erin E. Fox Cancer Epidemiology and Surveillance Branch, Texas Department of State Health Services
Scott Horel Department of Epidemiology and Biostatistics, Texas A&M University
Kimberly J. Johnson Division of Epidemiology/Clinical Research, Department of Pediatrics, University of Minnesota
Colleen McLaughlin New York State Cancer Registry, New York Department of Health
Beth A. Mueller Fred Hutchinson Cancer Research Center
Peggy Reynolds Northern California Cancer Center
Julie Von Behren Northern California Cancer Center
Logan G. Spector Division of Epidemiology/Clinical Research, Department of Pediatrics, University of Minnesota Masonic Cancer Center, University of Minnesota

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Childhood leukaemia following medical diagnostic exposure to ionizing radiation in utero or after birth

A statistical association between childhood leukaemia and an abdominal X-ray examination of the pregnant mother was first reported in 1956 from a case-control study of childhood cancer mortality conducted in Great Britain. This study, later called the Oxford Survey of Childhood Cancers (OSCC), was continued and eventually showed a highly statistically significant approximately 50% proportional increase in the risk of childhood leukaemia associated with antenatal diagnostic radiography. The association has been confirmed by many case-control studies carried out around the world, the appropriately combined results of which show a highly statistically significant increase in risk that is compatible with the OSCC finding. There is no doubt about the reality of the statistical association, but a causal interpretation has been questioned. On balance, however, the evidence points to low-level irradiation of the fetus increasing the risk of leukaemia in childhood, with an excess relative risk coefficient of around 50 Gy(-1) (equivalent to an excess absolute risk coefficient of about 3% Gy(-1)), although the uncertainty associated with these coefficients is considerable and they are likely to be overestimates. In contrast to exposure in utero, the evidence from case-control studies for an association between childhood leukaemia and postnatal exposure to medical diagnostic irradiation is equivocal and sometimes conflicting. Since standard radiation risk models predict that low-level exposure in the early years of life should produce an increased risk of childhood leukaemia that is roughly similar to that arising from fetal exposure, this absence of persuasive evidence is likely to be due to various problems with the studies. This is unfortunate given the rise in relatively high dose diagnostic procedures (e.g. paediatric CT scans) that would be predicted to materially increase the relative risk of childhood leukaemia.