Cancer in siblings of children with cancer in the Nordic countries: a population-based cohort study

Morbidity and health care use among siblings of children with cancer: A population-based study

BACKGROUND

Childhood cancer impacts the entire family unit. We sought to investigate its impact on the long-term physical health outcomes of siblings of children with cancer.

PROCEDURE

Pediatric cancer patients diagnosed in Ontario, Canada between 1988 and 2016 were linked to biological siblings. Sibling cases were matched to population controls based on sex, age, geographic location, and number of other children in the family. After individual linkage to health services data, we compared several outcomes between sibling cases and controls: (a) physical health conditions (such as diabetes, hypertension, and death); (b) acute health care use (hospitalization, low- and high-acuity emergency department [ED] visits); and (c) preventive health care use (periodic health checkups, influenza vaccinations). Cox proportional hazards, recurrent event, or logistic regression models were used as appropriate.

RESULTS

We identified 8529 sibling cases and 30,364 matched controls (median age at index: 6 years, median age at last follow-up 17 years). Compared to controls, siblings were at increased risk of hypertension (hazard ratio [HR] 1.8; 95% confidence interval [CI] 1.1-2.9; p = .01), had higher rates of low- and high-acuity ED visits (rate ratio 1.1; 95% CI 1.1-1.2; p < .001), and increased risk of hospitalization (HR 1.1; 95% CI 1.1-1.2; p < .001). Sibling cases were also more likely to receive preventive health care (p < .05).

CONCLUSION

Increased risk of hypertension, high-acuity ED visits, and hospitalizations suggest that siblings may experience poorer health compared to controls. Counseling families about this potential increased risk and long-term follow-up of siblings to monitor their physical health may be justified.

Family history of any cancer for childhood leukemia patients in Sweden

Acute lymphoblastic leukemia (ALL) is the most common childhood leukemia, while the other types, acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CML) are much rarer. While data on familial risks for childhood ALL have been emerging, such data for the other childhood leukemias are hardly available. We aim to fill in the gap of knowledge by assessing familial clustering of each childhood leukemia with childhood and adult leukemia and with any cancer. We identified 4461 childhood leukemias from the Swedish Cancer Registry and obtained their family members from the Multigeneration Register. Standardized incidence ratios (SIRs) were 3.34 for singleton siblings both diagnosed with ALL before age 20 years and 1.64 for those who had a family member diagnosed with ALL in adult age. Other childhood leukemias showed no familial risk, but childhood ALL risk was increased to 1.40 when adult family members were diagnosed with CLL. Childhood ALL was associated with endometrial cancer, and female ALL patients showed increased risk when family members were diagnosed with testicular cancer, melanoma, and skin squamous cell carcinoma. Childhood CLL was associated with rectal cancer, and childhood AML was associated with pancreatic and bladder cancers. As most of these associations are reported for the first time, there is a need to replicate the findings from independent sources.

Family history of early onset acute lymphoblastic leukemia is suggesting genetic associations

Childhood acute lymphoblastic leukemia (ALL) has an origin in the fetal period which may distinguish it from ALL diagnosed later in life. We wanted to test whether familial risks differ in ALL diagnosed in the very early childhood from ALL diagnosed later. The Swedish nation-wide family-cancer data were used until year 2016 to calculate standardized incidence ratios (SIRs) for familial risks in ALL in three diagnostic age-groups: 0–4, 5–34 and 35 + years. Among 1335 ALL patients diagnosed before age 5, familial risks were increased for esophageal (4.78), breast (1.42), prostate (1.40) and connective tissue (2.97) cancers and leukemia (2.51, ALL 7.81). In age-group 5–34 years, rectal (1.73) and endometrial (2.40) cancer, myeloma (2.25) and leukemia (2.00, ALL 4.60) reached statistical significance. In the oldest age-group, the only association was with Hodgkin lymphoma (3.42). Diagnostic ages of family members of ALL patients were significantly lower compared to these cancers in the population for breast, prostate and rectal cancers. The patterns of increased familial cancers suggest that BRCA2 mutations could contribute to associations of ALL with breast and prostate cancers, and mismatch gene PMS2 mutations with rectal and endometrial cancers. Future DNA sequencing data will be a test for these familial predictions.

Health-related and cancer risk concerns among siblings of childhood cancer survivors: a report from the Childhood Cancer Survivor Study (CCSS)

OBJECTIVE

To characterize the prevalence and predictors of concerns regarding future health and cancer risk among siblings of childhood cancer survivors.

METHODS

This study reports longitudinal data (baseline and follow-up) from 3969 adult siblings (median age = 29 [range 18-56] years) of long-term survivors of childhood cancer (median time since diagnosis 19.6 [9.6-33.8] years). Self-reported future health and cancer risk concerns (concerned vs not concerned) were assessed. Demographics and health data reported by both the siblings and their matched cancer survivors were examined as risk factors for health concerns using multivariable logistic regression.

RESULTS

Percentage of siblings reporting future health and cancer risk concerns, respectively, decreased across decade of survivors' diagnosis: 1970s (73.3%; 63.9%), 1980s (67.2%; 62.6%), and 1990s (45.7%; 52.3%). Risk factors associated with future health concerns included sibling chronic health conditions (grade 2 Odds Ratio [OR]=1.57, 95% CI: 1.12-2.20; grades 3-4 OR=1.86, 95% CI: 1.18-2.94; compared to less than grade 2). Risk factors associated with future cancer concerns included sibling chronic health conditions (grade 2 OR=1.43, 95% CI: 1.05-1.94; grades 3-4 OR=1.64, 95% CI: 1.09-2.47; compared to less than grade 2).

CONCLUSIONS

Sibling concerns regarding future health and cancer have diminished in recent decades. There are subgroups of siblings that are at-risk for future health and cancer risk concerns.

IMPLICATIONS FOR CANCER SURVIVORS

Routine screening of concerns in at-risk siblings of survivors of childhood cancer may benefit the siblings of cancer survivors. These individuals may benefit from early interventions during diagnosis and treatment of their siblings.

Increased Cancer Risk in Families with Pediatric Cancer Is Associated with Gender, Age, Diagnosis, and Degree of Relation to the Child

BACKGROUND

Studies of cancer risk among relatives of children with cancer beyond parents and siblings are limited. We have investigated the cancer risk up to the third degree of relation in families with pediatric cancer to reveal patterns of inheritance.

METHODS

A single-center cohort of 757 patients with pediatric cancer was linked to the Swedish National Population Register, resulting in 16,137 relatives up to the third degree of relation. All relatives were matched to the Swedish Cancer Register, and standard incidence ratios (SIR) were calculated to define relatives at risk.

RESULTS

Children and adults up to the third degree of relation had increased cancer risk, with SIRs of 1.48 (P = 0.01) and 1.07 (P < 0.01), respectively. The SIRs for first- and third-degree adult relatives were 1.22 and 1.10, respectively, but no increased risk was observed in second-degree relatives. Male relatives had a higher risk than females, especially when related to a girl and when the child had leukemia. The risk was mainly increased for lung, prostate, and gastrointestinal cancer. When excluding 29 families of children with known pathogenic germline variants, the increased risk remained.

CONCLUSIONS

Relatives to children with cancer up to third degree of relation have an increased cancer risk. Known pathogenic germline variants do not explain this increased risk.

IMPACT

The overall increased cancer risk among relatives of children with cancer in this population-based cohort strengthens the importance of surveillance programs for families with pediatric cancer.

The joy and duty of a marginal teratologist

On the occasion of this anniversary of the Society for Birth Defects Research and Prevention, I accept the invitation to offer personal reflections on the earlier days of the Society and the importance of the discipline. My focus is on what few contributions I have offered, but more, on the value of having the teratologist's perspective on other aspects of my career in medical genetics and genetic epidemiology. Treating my professional life as a development biologist (of which teratologists are a breed), I recount the institutions I have been at, but more importantly, the people I have been influenced by, more often than not accomplished teratologists. The one big thought I wish to leave is the primacy and criticality of being mentored and mentoring at ALL stages of a career.

Linking population-based registries to identify familial cancer risk in childhood cancer

BACKGROUND

Linked population-based registries provide a unique source for identification of new family cancer syndromes and for elucidating risk of early-onset cancer in close relatives of cancer patients.

METHODS

Using the Finnish Cancer Registry, we identified 9078 probands who had been diagnosed with cancer at <21 years of age between 1970 and 2012. Siblings, offspring, parents, nephews, and nieces of probands were identified from the Population Registry. Childhood and young adult (ChYA) cancer diagnoses (age 0-39 years) in relatives were identified by linking to the Finnish Cancer Registry. The relative risk of ChYA cancer in family members of probands was estimated using standardized incidence ratios (SIRs).

RESULTS

Among 58,010 family members of the 9078 probands, 363 ChYA cancers were diagnosed, 324 of which were expected (SIR, 1.12; 95% CI, 1.01-1.24). The risk of ChYA cancer was elevated both in offspring (SIR, 2.25; 95% CI, 1.51-3.24) and in siblings (SIR, 1.17; 95% CI, 1.01-1.36). Offspring of probands with retinoblastoma were at highest risk (SIR, 75.85; 95% CI, 32.75-149.45); risks were also elevated for siblings of probands with lymphoma (SIR, 1.62; 95% CI, 1.14-2.25). Known cancer predisposition syndromes were observed in 29 (66%) of 44 sibling pairs with cancers diagnosed at <21 years of age and in 20% of the 135 families with a childhood cancer proband whose sibling was diagnosed with a young adult malignancy.

CONCLUSION

Linked population-based registry data indicate a modestly increased risk of ChYA in relatives of children with cancer. Some of the observed cancer clusters in the cohort suggest novel patterns and familial cancer syndromes.

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.

Family history of cancer and the risk of childhood solid tumours: a Norwegian nationwide register-based cohort study

Background:

It is not clear if family history of cancer increases risk of cancer in children.

Methods:

We followed-up a total of 2 610 937 children born between 1960 and 2001 for cancer risk, and their parents and siblings. In this period, 2477 primary childhood solid tumours (except lymphoma) were diagnosed. The data from the Norwegian Family and Life Course Study and from the Norwegian Cancer Register were used. Classification of hereditary cancer syndromes was based on tumour histology, pedigrees and Chompret’s criteria.

Results:

An association between risk of childhood tumours and first-degree family history of early onset of solid tumours was observed for central nervous system tumours (2.3-fold), neuroblastoma (2.3-fold), retinoblastoma (6.1-fold), hepatic tumours (4.0-fold), and melanomas (8.3-fold). Elevated risk was also seen for osteosarcomas (1.5-fold) when considering first-degree family history of cancer diagnosed at any age. The risk of hepatic tumours, neuroblastomas and melanomas remained elevated even after controlling for probable hereditary cancer syndromes.

Conclusions:

The increased risk for several childhood solid site cancers among those with first-degree relatives diagnosed with solid cancer suggests that genetic or environmental factors are involved. The fact that these associations remained after controlling for hereditary cancer syndromes indicates other genetic mechanisms might be involved.

Predominance of girls with cancer in families with multiple childhood cancer cases

Background

Recent studies indicate that one of four childhood cancers can be attributed to hereditary genetic abnormalities.

Methods

The Lund Childhood Cancer Genetic study includes newly diagnosed childhood cancer patients as well as childhood cancer survivors visiting the Department of Pediatrics or the Late Effect Clinic at Skåne University Hospital, Lund, Sweden. Questionnaires regarding family history of cancer and blood samples were provided. Reported data were validated and extended by use of the Swedish Population- and Cancer Registries. Demographics in families with one case of childhood cancer (FAM1) were investigated and compared to families with multiple cases of childhood cancer (FAM > 1) as well as to childhood cancer in the general population.

Results

Forty-one out of 528 families (7.8%) had more than one case of childhood cancer. In 23 families the affected children were relatives up to a 3rd degree (4.4%). In FAM > 1, 69.2% of the children with leukemia and 60% of those with tumors in the central nervous system (CNS) had a childhood relative with matching diagnosis, both significantly higher than expected. Significantly more female than male patients were observed in FAM > 1 compared to FAM1. This female predominance was most striking in childhood leukemia (77% female) and also, yet to a lesser extent, in CNS tumors (68% female).

Conclusions

We conclude that the high proportion of children with leukemia or CNS tumors in FAM > 1 having a childhood relative with the same diagnosis suggests a hereditary background. Moreover, we report a female predominance in childhood leukemia and childhood CNS tumors in FAM > 1, which may indicate a hereditary gender-specific risk factor in these families.

Incorporation of the time aspect into the liability-threshold model for case-control-family data

Familial aggregation and the role of genetic and environmental factors can be investigated through family studies analysed using the liability-threshold model. The liability-threshold model ignores the timing of events including the age of disease onset and right censoring, which can lead to estimates that are difficult to interpret and are potentially biased. We incorporate the time aspect into the liability-threshold model for case-control-family data following the same approach that has been applied in the twin setting. Thus, the data are considered as arising from a competing risks setting and inverse probability of censoring weights are used to adjust for right censoring. In the case-control-family setting, recognising the existence of competing events is highly relevant to the sampling of control probands. Because of the presence of multiple family members who may be censored at different ages, the estimation of inverse probability of censoring weights is not as straightforward as in the twin setting but requires consideration. We propose to employ a composite likelihood conditioning on proband status that markedly simplifies adjustment for right censoring. We assess the proposed approach using simulation studies and apply it in the analysis of two Danish register-based case-control-family studies: one on cancer diagnosed in childhood and adolescence, and one on early-onset breast cancer. Copyright © 2017 John Wiley & Sons, Ltd.

Pediatric T-cell acute lymphoblastic leukemia

The most common pediatric malignancy is acute lymphoblastic leukemia (ALL), of which T-cell ALL (T-ALL) comprises 10-15% of cases. T-ALL arises in the thymus from an immature thymocyte as a consequence of a stepwise accumulation of genetic and epigenetic aberrations. Crucial biological processes, such as differentiation, self-renewal capacity, proliferation, and apoptosis, are targeted and deranged by several types of neoplasia-associated genetic alteration, for example, translocations, deletions, and mutations of genes that code for proteins involved in signaling transduction, epigenetic regulation, and transcription. Epigenetically, T-ALL is characterized by gene expression changes caused by hypermethylation of tumor suppressor genes, histone modifications, and miRNA and lncRNA abnormalities. Although some genetic and gene expression patterns have been associated with certain clinical features, such as immunophenotypic subtype and outcome, none has of yet generally been implemented in clinical routine for treatment decisions. The recent advent of massive parallel sequencing technologies has dramatically increased our knowledge of the genetic blueprint of T-ALL, revealing numerous fusion genes as well as novel gene mutations. The challenges now are to integrate all genetic and epigenetic data into a coherent understanding of the pathogenesis of T-ALL and to translate the wealth of information gained in the last few years into clinical use in the form of improved risk stratification and targeted therapies. Here, we provide an overview of pediatric T-ALL with an emphasis on the acquired genetic alterations that result in this disease. © 2016 Wiley Periodicals, Inc.

Cancer risk in siblings of children with congenital malformations

PURPOSE

Cancer and birth defects cluster in families more often than expected by chance, but the reasons are neither well known nor well studied.

METHODS

From singletons born alive in Denmark between 1 January 1977 and 31 December 2007, we identified children who had no congenital malformations but had a full or half sibling with a congenital malformation (CM) diagnosed in the first year of life; this constituted the exposed group, while children whose siblings had no such condition constituted a reference group. We estimated cancer risks for children who had a full sibling or a half sibling with a CM using a Cox proportional hazards regression model. To control for confounding related to change of family structure, we estimated cancer risks for children from core families and children from broken families separately. Children were followed from birth up to 30 years of age (median follow-up 13.6 years). We obtained information on CMs and cancer from the Danish National Hospital Register and the Danish Cancer Registry.

RESULTS

We identified 991,454 (78%) children from core families with 53,995 children who had a full sibling with a CM and 277,773 (22%) children from broken families with 7200 children who had a full sibling with a CM and 6194 children who had a half sibling with a CM. Children who had a full sibling with a CM from both core and broken families showed, in general, no increased cancer risk compared with children whose siblings had no CM, except in the case of children who had a full sibling with a CM in the nervous system (HR=2.61, 95%CI:1.60-4.27) or in the eye, ear, face, or neck (HR=2.47, 95%CI: 1.46-4.18). Children who had a half sibling with a CM seemed to have a higher cancer risk in early adulthood (HR=1.87, 95%CI: 0.98-3.56).

CONCLUSIONS

Children who had a full sibling with a CM had no increased risk of cancer except for those who had a full sibling with a CM in the nervous system or in the eye, ear, face or neck. Children with a half-sibling with a CM tended to have an increased cancer risk in early adulthood, perhaps a result of chance. This study should be replicated using other data sources.

Treatment-related toxicities in children with acute lymphoblastic leukaemia predisposition syndromes

Although most children with acute lymphoblastic leukaemia (ALL) do not harbor germline mutations that strongly predispose them to development of this malignancy, large syndrome registries and detailed mapping of exomes or whole genomes of familial leukaemia kindreds have revealed that 3-5% of all childhood ALL cases are due to such germline mutations, but the figure may be higher. Most of these syndromes are primarily characterized by their non-malignant phenotype, whereas ALL may be the dominating or even only striking manifestation of the syndrome in some families. Identification of such ALL patients is important in order to adjust therapy and offer genetic counseling and cancer surveillance to mutation carriers in the family. In the coming years large genomic screening projects are expected to reveal further hitherto unrecognised familial ALL syndromes. The treatment of ALL cases harboring cancer predisposing mutations can be challenging for both the physician and the patient due to their preexisting symptoms, their reduced tolerance to radio- and/or chemotherapy with enhanced risk of life-threatening organ toxicities, and the paucity of data from ALL patients with the same or similar syndromes being treated by contemporary protocols. Recent studies clearly indicate that many of these patients stand a good chance of cure, and that they should be offered chemotherapy with the intention to cure. Some of these syndromes are characterized by reduced tolerance to radiotherapy and/or specific anticancer agents, while others are not. This review summarises our current knowledge on the risk of acute toxicities for these ALL patients and provides guidance for treatment adjustments.

Perinatal and familial risk factors for acute lymphoblastic leukemia in a Swedish national cohort

BACKGROUND

Perinatal factors including high birth weight have been found to be associated with acute lymphoblastic leukemia (ALL) in case-control studies. However, to the best of our knowledge, these findings have seldom been examined in large population-based cohort studies, and the specific contributions of gestational age and fetal growth remain unknown.

METHODS

The authors conducted a national cohort study of 3,569,333 individuals without Down syndrome who were born in Sweden between 1973 and 2008 and followed for the incidence of ALL through 2010 (maximum age, 38 years) to examine perinatal and familial risk factors.

RESULTS

There were 1960 ALL cases with 69.7 million person-years of follow-up. After adjusting for potential confounders, risk factors for ALL included high fetal growth (incidence rate ratio [IRR] per additional 1 standard deviation, 1.07; 95% confidence interval [95% CI], 1.02-1.11 [P =.002]; and IRR for large vs appropriate for gestational age, 1.22; 95% CI, 1.06-1.40 [P =.005]), first-degree family history of ALL (IRR, 7.41; 95% CI, 4.60-11.95 [P<.001]), male sex (IRR, 1.20; 95% CI, 1.10-1.31 [P<.001]), and parental country of birth (IRR for both parents born in Sweden vs other countries, 1.13; 95% CI, 1.00-1.27 [P =.045]). These risk factors did not appear to vary by patient age at the time of diagnosis of ALL. Gestational age at birth, season of birth, birth order, multiple birth, parental age, and parental education level were not found to be associated with ALL.

CONCLUSIONS

In this large cohort study, high fetal growth was found to be associated with an increased risk of ALL in childhood through young adulthood, independent of gestational age at birth, suggesting that growth factor pathways may play an important long-term role in the etiology of ALL.

Concordant B-cell precursor acute lymphoblastic leukemia in non-twinned siblings

Associating the risk of childhood acute lymphoblastic leukemia (ALL) with genetic predisposition is still a challenge. Here, we discuss two non-twinned sibs (girl and boy) diagnosed with B-cell precursor (BCP-ALL) and ETV6-RUNX1. BCP-ALL clinical onset occurred 10months apart from each diagnosis. One child is alive in complete continuous remission, whereas, the other relapsed and evolved to death with resistance to ALL treatment. Despite the fact that BCP-ALL with ETV6-RUNX1 usually results in a very good prognosis, the sibs experienced divergent outcomes; a remarkable difference in one child that presented a more aggressive disease was higher leukocytosis associated with IKZF1 deletion. The familial history of cancer and genetic susceptibility was explored. The sibs were absolutely identical in all 17 loci of genes tested; GSTM1, GSTT1, NQO1, TP53, and TP63 were wild-type, whereas at least one copy of the variant allele for IKZF1, ARID5B, PTPRJ and CEBPE was present. The familial pattern of ETV6 was tested by the 12p microsatellite analysis and demonstrated that deletions occurred in one child but not the other, while heterozygous patterns were found in the parents. Altogether, our data suggest that genetic predisposition aligned with chance haa an additive effect in BCP-ALL outcome.

Cancer risks for relatives of children with cancer

We determined the extent and distribution of cancers in relatives of 379 children newly diagnosed with cancer. Family history was collected from 1,337 first-degree and 3,399 second-degree relatives and incidence compared with national age- and gender-specific rates. Overall, 14 children (3.7%) had a relative with a history of childhood cancer and 26 children (6.9%) had a first-degree relative with a history of cancer, with only one of these having an identifiable familial cancer syndrome. There was a higher than expected incidence of childhood cancer among first-degree relatives (parents and siblings) (standardized incidence ratio (SIR) 1.43; 95% CI 0.54–5.08). There was also a higher than expected incidence of adult cancers among first-degree relatives (SIR 1.45; 95% CI 0.93–2.21), particularly in females (SIR 1.82; 95% CI 1.26–3.39). The increased family cancer history in first-degree females was largely attributable to an effect in mothers (SIR 1.78; 95% CI 1.27–3.33). The gender-specific association was reflected in higher than expected incidence rates of breast cancer in both mothers (SIR 1.92; 95% CI 0.72–6.83) and aunts (SIR 1.64; 95% CI 0.98–2.94). These findings support the hypothesis that previously undetected familial cancer syndromes contribute to childhood cancer.

Familial aggregation of childhood and adult cancer in the Utah genealogy

A small proportion of childhood cancer is attributable to known hereditary syndromes, but whether there is any familial component to the remainder remains uncertain. We explored familial aggregation of cancer in a population-based case-control study using genealogical record linkage and designed to overcome limitations of previous studies. Subjects were selected from the Utah Population Database. We compared risk of cancer in adult first-degree relatives of children who were diagnosed with cancer with the risk in relatives of children who had not had a cancer diagnosed. We identified 1,894 childhood cancer cases and 3,788 controls; 7,467 relatives of cases and 14,498 relatives of controls were included in the analysis. Relatives of children with cancer had a higher risk of cancer in adulthood than relatives of children without cancer [odds ratio (OR) 1.31, 95% confidence interval (CI) 1.11-1.56]; this was restricted to mothers and siblings and was not evident in fathers. Familial aggregation appeared stronger among relatives of cases diagnosed before 5 years of age (OR 1.48, 95% CI 1.13-1.95) than among relatives of cases who were older when diagnosed (OR 1.22, 95% CI 0.98-1.51). These findings provide evidence of a generalized excess of cancer in the mothers and siblings of children with cancer. The tendency for risk to be higher in the relatives of children who were younger at cancer diagnosis should be investigated in other large data sets. The excesses of thyroid cancer in parents of children with cancer and of any cancer in relatives of children with leukemia merit further investigation.

Familial risk of childhood cancer and tumors in the Li-Fraumeni spectrum in the Utah Population Database: implications for genetic evaluation in pediatric practice

We used the Utah Population Database to examine risk of cancer in relatives of 4,482 pediatric cancer cases (≤18 years old) diagnosed from 1966 to 2009 compared to matched population controls. We quantified cancer risk in relatives of children with cancer to determine evidence of familial aggregation and to inform risk assessment and counseling for families. Odds ratios that reflect risk were obtained using conditional logistic regression models adjusting for number of biological relatives, their degree of genetic relatedness and their person-years at risk. First-degree relatives (primarily siblings) of pediatric cases faced a twofold increased risk of a cancer diagnosis before age 19, which extended to their second-degree relatives (p < 10(-4), respectively). Furthermore, first-degree relatives of children diagnosed before age 5 had a 3.6-fold increased risk of developing pediatric cancer (p < 10(-7)), second-degree relatives of very young (under age 5) cases were at 2.5-fold risk (p < 10(-4)) and third-degree relatives were at twofold risk (P < 10(-3)) of childhood cancer. Although first-degree relatives of pediatric cases have a slight increased risk of adult tumors, when they do develop cancer they have a 1.7-fold risk of developing a tumor in the Li-Fraumeni spectrum. Our findings support the hypothesis of familial aggregation in pediatric cancer and suggest that a higher percent of childhood cancers may be related to hereditary syndromes than are adult cancers. We encourage the collection of a family medical history that is routinely updated for all pediatric cancer patients, and that families with early-onset adult cancers or clusters of several cancers are referred for genetic counseling.

Rare allelic forms of PRDM9 associated with childhood leukemogenesis

One of the most rapidly evolving genes in humans, PRDM9, is a key determinant of the distribution of meiotic recombination events. Mutations in this meiotic-specific gene have previously been associated with male infertility in humans and recent studies suggest that PRDM9 may be involved in pathological genomic rearrangements. In studying genomes from families with children affected by B-cell precursor acute lymphoblastic leukemia (B-ALL), we characterized meiotic recombination patterns within a family with two siblings having hyperdiploid childhood B-ALL and observed unusual localization of maternal recombination events. The mother of the family carries a rare PRDM9 allele, potentially explaining the unusual patterns found. From exomes sequenced in 44 additional parents of children affected with B-ALL, we discovered a substantial and significant excess of rare allelic forms of PRDM9. The rare PRDM9 alleles are transmitted to the affected children in half the cases; nonetheless there remains a significant excess of rare alleles among patients relative to controls. We successfully replicated this latter observation in an independent cohort of 50 children with B-ALL, where we found an excess of rare PRDM9 alleles in aneuploid and infant B-ALL patients. PRDM9 variability in humans is thought to influence genomic instability, and these data support a potential role for PRDM9 variation in risk of acquiring aneuploidies or genomic rearrangements associated with childhood leukemogenesis.

Familial risks for childhood acute lymphocytic leukaemia in Sweden and Finland: far exceeding the effects of known germline variants

Despite recent successes in the identification of genetic susceptibility loci, no familial risk has been demonstrated for childhood acute lymphoblastic leukaemia (ALL). We identified 3994 childhood ALL cases from two cancer registries; family members were obtained from population registers. The standardized incidence ratio for familial risk in singleton siblings and twins was 3·2 (95% confidence interval 1·5-5·9) and 162·6 (70·2-320·4), respectively. The present data constitute the first demonstration of familial risk for singleton siblings; the high risk for twins is believed to result from shared prenatal blood circulation. The data suggest that currently unidentified genetic loci underlie these observed familial effects.

Reliability of cancer family history reported by parents in a case-control study of childhood leukemia

PURPOSE

To investigate the reliability of family history of cancer reported by parents of children with acute lymphoblastic leukemia (ALL) and parents of healthy control children.

METHODS

A total of 301 parents were selected based on positive or negative family history of cancer at baseline, case-control status, and gender of the respondent (mother or father). Baseline responses were compared with responses at the second interview using the same questionnaire. Reliability was measured using proportion of overall agreement, Cohen's kappa, and Cronbach's alpha; a logistic regression model was also used to assess the role of the case-control status on overall agreement as the dependent variable.

RESULTS

The overall agreement between interviews was high and similar for cases (85 %) and controls (86 %); there were no consistent effects of respondent gender, age at first interview, or time elapsed between interviews on agreement measures. Agreement measures did not materially vary according to whether respondents were reporting about their mothers, fathers, or siblings.

CONCLUSIONS

The study showed very good reliability of reporting family history among young parents of children affected with leukemia and parents of healthy control children.

Increased incidence of childhood, prostate and breast cancers in relatives of childhood cancer patients

Whether cancer predisposing familial factors are associated with childhood tumors is unclear. The purpose was to study the incidence of childhood and adult tumors in extended families of children with cancer. Family history of cancer was obtained through questionnaires, and the Swedish Population-, and Cancer Registries for 194 childhood cancer patients aged ≤18 years, diagnosed 1972-2009. Standardized cancer incidence ratios (SIR), and 95% confidence intervals (CI) were estimated and compared with expected rates. Overall, 21 of the 194 patients had any relative with a childhood tumor. When restricted to first- to third degree relatives, increased incidences of childhood (SIR: 2.5; 95% CI: 1.3-4.4) and adult tumors (SIR: 1.5; 95% CI: 1.3-1.7), especially in the prostate (SIR: 2.7; 95% CI: 1.9-3.8) and breast (SIR: 1.7; 95% CI: 1.2-2.4) were observed. Prostate and breast cancers were observed at earlier than average ages. No TP53 mutations or known cancer predisposing syndromes were found in families with multiple childhood tumors. Familial factors may increase the risk for childhood cancer and modify the age of onset of common adult tumors. Studying extended families with multiple childhood tumors may be a valuable approach to understanding the etiology of childhood tumors.

Cancer prevention and screening practices of siblings of childhood cancer survivors: a report from the Childhood Cancer Survivor Study

BACKGROUND

To compare the skin and breast/cervical cancer prevention/screening practices of adult siblings of childhood cancer survivors with controls and to identify modifying factors for these practices.

METHODS

Cross-sectional, self-report data from 2,588 adult siblings of 5+ year survivors of childhood cancer were analyzed to assess cancer prevention/screening practices. Two age, sex, and race/ethnicity-matched samples (N = 5,915 and N = 37,789) of the Behavioral Risk Factor Surveillance System participants served as the comparison populations. Sociodemographic and cancer-related data were explored as modifying factors for sibling cancer prevention/screening practices through multivariable logistic regression.

RESULTS

Compared with controls, siblings were more likely to practice skin cancer prevention behaviors: use of protective clothing [OR, 2.85; 95% confidence interval (CI), 2.39-3.39], use of shade (OR, 2.11; 95% CI, 1.88-2.36), use of sunscreen (OR, 1.27; 95% CI, 1.14-1.40), and wearing a hat (OR, 1.77; 95% CI, 1.58-1.98). No differences were noted for breast/cervical cancer screening including mammography and Pap testing. Having less than a high school education and lack of health insurance were associated with diminished cancer prevention/screening behaviors. Survivor diagnosis, treatment intensity, adverse health, chronic health conditions, and second cancers were not associated with sibling cancer prevention/screening behaviors.

CONCLUSIONS

Siblings of cancer survivors report greater skin cancer prevention practices when compared with controls; however, no differences were noted for breast/cervical cancer screening practices. Access to care and lack of education may be associated with decreased cancer prevention/screening behaviors. Interventions are needed to address these barriers.

IMPACT

Research should be directed at understanding the impact of the cancer experience on sibling health behaviors.

Genetic disease in the children of Danish survivors of childhood and adolescent cancer

PURPOSE

Preconception radiation and chemotherapy have the potential to produce germ cell mutations leading to genetic disease in the next generation. Dose-response relationships were evaluated between cancer treatments and untoward pregnancy outcomes.

PATIENTS AND METHODS

A case-cohort study was conducted involving 472 Danish survivors of childhood and adolescent cancer and their 1,037 pregnancies. Adverse outcomes included 159 congenital malformations, six chromosomal abnormalities, seven stillbirths, and nine neonatal deaths. Preconception radiation doses to the gonads, uterus, and pituitary gland and administered chemotherapy were quantified based on medical records and related to adverse outcomes using a generalized estimating equation model.

RESULTS

No statistically significant associations were found between genetic disease in children and parental treatment with alkylating drugs or preconception radiation doses to the testes in male and ovaries in female cancer survivors. Specifically, the risk of genetic disease was similar among the children of irradiated survivors when compared with nonirradiated survivors (relative risk [RR], 1.02; 95% CI, 0.59 to 1.44; P = .94). A statistically significant association between abdomino-pelvic irradiation and malformations, stillbirths, and neonatal deaths was not seen in the children of female survivors overall (P = .07) or in the children of mothers receiving high uterine doses (mean, 13.5 Gy; max, 100 Gy; RR, 2.3; 95% CI, 0.95 to 5.56).

CONCLUSION

Mutagenic chemotherapy and radiotherapy doses to the gonads were not associated with genetic defects in children of cancer survivors. However, larger studies need to be conducted to further explore potential associations between high-dose pelvic irradiation and specific adverse pregnancy outcomes.

Family history of cancer and non-malignant diseases and risk of childhood acute lymphoblastic leukemia: a Children's Oncology Group Study

BACKGROUND

Studies of family history of cancer and non-malignant diseases in childhood acute lymphoblastic leukemia (ALL) show inconsistent findings. Most studies show no increased risk with family history of cancer. Non-malignant diseases such as allergic diseases, autoimmune diseases, birth defects and thyroid diseases have been reported to be associated with ALL.

METHODS

We conducted a case-control study of family history of cancer and selected non-malignant conditions (allergic diseases, autoimmune diseases, birth defects, and thyroid diseases). ALL cases were obtained from Children's Cancer Group institutions from January 1989 to June 1993. Controls were recruited via random digit dialing. Family history for first degree relatives and grandparents of ALL cases and controls was collected by structured telephone questionnaires. Conditional logistical regression was used to calculate odds ratios adjusting for potential confounders.

RESULTS

We found a borderline association of ALL and having a family member with a history of cancer in cases (n=1842) compared to controls (n=1986) (OR=0.98, 95%CI=0.93, 1.00) and an inverse association for esophageal cancer based on small numbers. Family history of food and drug allergies demonstrated a modestly reduced risk (OR=0.83, 95%CI=0.73, 0.95) as did family history of rheumatoid arthritis (OR=0.79, 95%CI=0.65, 0.96). There were no associations with family history of any autoimmune diseases, immunodeficiencies, birth defects, thyroid diseases and risk of childhood ALL.

CONCLUSIONS

These results show no association of overall family history of cancer with childhood ALL, while providing additional evidence for an inverse association with family history of allergic disease. Two potentially new associations of ALL with family history of esophageal cancer and rheumatoid arthritis require confirmation in other studies and validation with medical records.

High concordance of subtypes of childhood acute lymphoblastic leukemia within families: lessons from sibships with multiple cases of leukemia

Polymorphic genes have been linked to the risk of acute lymphoblastic leukemia (ALL). Surrogate markers for a low burden of early childhood infections are also related to increased risk for developing childhood ALL. It remains uncertain, whether siblings of children with ALL have an increased risk of developing ALL. This international collaboration identified 54 sibships with two (N = 51) or more (N = 3) cases of childhood ALL (ages <18 years). The 5-year event-free survival for 61 patients diagnosed after 1 January 1990 was 0.83 ± 0.05. Ages at diagnosis (Spearman correlation coefficient, r(S) = 0.41, P = 0.002) were significantly correlated, but not WBCs (r(S) = 0.23, P = 0.11). In 18 sibships with successful karyotyping in both cases, six were concordant for high-hyperdiploidy (N = 3), t(12;21) [ETV6/RUNX1] (N = 1), MLL rearrangement (N = 1) or t(1;19)(q23/p13) (N = 1). Eleven sibships were ALL-subtype concordant, being T-cell ALL (T-ALL) (N = 5, of a total of six sibships, where the first-born had T-ALL) or B-lineage ALL belonging to the same cytogenetic subset (N = 6), a finding that differs significantly from the expected chance distribution (κ: 0.58; P < 0.0001). These data indicate strong genetic and/or environmental risk factors for childhood ALL that are restricted to specific ALL subtypes, which must be taken into account, when performing epidemiological studies to reveal etiological factors.

Familial risks in nervous system tumours: joint Nordic study

Background:

Familial nervous system cancers are rare and limited data on familial aspects are available particularly on site-specific tumours.

Methods:

Data from five Nordic countries were used to analyse familial risks of nervous system tumours. Standardised incidence ratios (SIRs) were calculated for offspring of affected relatives compared with offspring of non-affected relatives.

Results:

The total number of patients with nervous system tumour was 63 307, of whom 32 347 belonged to the offspring generation. Of 851 familial patients (2.6%) in the offspring generation, 42 (4.7%) belonged to the families of a parent and at least two siblings affected. The SIR of brain tumours was 1.7 in offspring of affected parents; it was 2.0 in siblings and 9.4 in families with a parent and sibling affected. For spinal tumours, the SIRs were much higher for offspring of early onset tumours, 14.0 for offspring of affected parents and 22.7 for siblings. The SIRs for peripheral nerve tumours were 16.3 in offspring of affected parents, 27.7 in siblings and 943.9 in multiplex families.

Conclusion:

The results of this population-based study on medically diagnosed tumours show site-, proband- and age-specific risks for familial tumours, with implications for clinical genetic counselling and identification of the underlying genes.

The Swedish Family-Cancer Database 2009: prospects for histology-specific and immigrant studies

The Swedish Family-Cancer Database comprises a total of 11.8 million individuals covering the Swedish population of the past 100 years. Version VIII of the Database is described in the present article. Cancer cases were retrieved from the Swedish Cancer Registry for the period 1958-2006, including more than 1 million first primary cancers. The number of familial cancers in offspring is 14,000 when a parent was diagnosed with a concordant (same) cancer and the number of concordant siblings was 6,000. From the year 1993 onwards histopathological data according to the SNOMED classification were used, which entails advantages for certain cancers, such as breast cancer. Even though the specific morphological classification only covers a limited number of years, it does cover most familial cancers in the offspring generation. The Database records the country of birth for each subject. A total of 1.79 million individuals were foreign born, Finns and other Scandinavians being the largest immigrant groups. The cancer incidence in the first-generation immigrants was compared to that in native Swedes using standardised incidence ratios (SIRs) to measure relative risk. The SIRs ranged widely between the immigrant groups, from 1.9-fold for myeloma to 25-fold for melanoma. The differences in SIRs were smaller in the second-generation immigrants. The usefulness and the possible applications of the Family-Cancer Database have increased with increasing numbers of cases, and the numerous applications have been described in some 300 publications. Familial cancer studies are in the stimulating interphase of the flourishing disciplines of genetics and epidemiology.

Lifelong cancer incidence in 47,697 patients treated for childhood cancer in the Nordic countries

BACKGROUND

The pattern of cancer in long-term survivors from childhood cancer has not been investigated comprehensively.

METHODS

We obtained a cohort of 47,697 children and adolescents aged 0-19 years with cancer as defined by the country-wide cancer registries of Denmark, Finland, Iceland, Norway, and Sweden during 1943-2005. Cohort members were followed through age 79 years for subsequent primary cancers notified to the registries, and the age-specific risk pattern of the survivors was compared with that of the national populations using country and sex standardized incidence ratios (SIRs). We used a multiplicative Poisson regression model to estimate relative risk of cancer for attained age, with adjustment for calendar period and age at diagnosis of primary cancer. We also calculated excess absolute risk (EAR) attributable to status as childhood cancer survivor and determined the cumulative incidence of second primary cancer as a function of attained age for three subcohorts defined by period of treatment for childhood cancer.

RESULTS

A total of 1180 asynchronous second primary cancers were observed in 1088 persons, yielding an overall SIR of 3.3 (95% confidence interval = 3.1 to 3.5). The relative risk was statistically significantly increased in all age groups, even for cohort members approaching 70 years of age. The EAR for second primary cancer among survivors increased gradually from one additional case per 1000 person-years of observation in early life to six additional cases per 1000 person-years in the age group 60-69 years. For children treated in the prechemotherapy era (1943-1959), the cumulative risk for a second primary cancer reached 18%, 34%, and 48% at ages 60, 70, and 80 years, respectively. The age-specific incidence rates were highest for cohort members treated in the era of intensive, multiple-agent chemotherapy (1975-2005).

CONCLUSION

Survivors of childhood cancer have a persistent excess risk for a second primary cancer throughout their lives, accompanied by continuous changes in the risk of cancers at specific sites.

Familial risks in nervous-system tumours: a histology-specific analysis from Sweden and Norway

BACKGROUND

There are limited data available on tumour subtype-specific familial risks for nervous-system tumours. We aimed to provide such data at the population level.

METHODS

We used data from the nationwide Swedish and Norwegian databases on familial cancer to calculate standardised incidence ratios (SIRs) for the familial risk of developing a nervous-system tumour in offspring born after 1931 (Sweden) or 1900 (Norway) whose parents or siblings were probands.

FINDINGS

54 195 patients had nervous-system tumours, 22 331 of whom belonged to the offspring generation aged 0-72 years in Sweden and 0-51 years in Norway. Of 709 familial patients in the offspring generation, 438 (61.8%) had a parent affected by a nervous-system tumour (SIR 1.66; 95% CI 1.51-1.82), 236 (33.3%) had a sibling affected by a nervous-system tumour (SIR 2.01; 95% CI 1.76-2.28), and 35 (4.9%) belonged to families with a parent and at least two siblings affected by a nervous-system tumour (multiplex families; SIR 13.40; 95% CI 9.33-18.66). The SIR for glioma was 1.8 (1.5-2.0) when a parent was a proband, but increased to 11.2 (5.7-19.5) in multiplex families. Early-onset neurinoma and haemangioma showed high familial risks; with an SIR for neurinoma of 1.7 (1.4-2.2) for offspring of affected parents, 2.7 (2.0-3.5) for siblings, and 27.2 (13.5-48.8) for multiplex families, and an SIR for haemangioma of 2.4 (1.4-3.8) for offspring of affected parents. Histology-specific population-based familial risks were shown for meningioma (1.6 for offspring of affected parents; 95% CI 1.3-2.0), ependymoma (2.7 for young offspring <20 years; 1.1-5.5), medulloblastoma (4.1 for siblings; 1.7-8.1), and neuroblastoma (3.2 for siblings; 1.1-6.9).

INTERPRETATION

Our results suggest a complex genetic background for nervous-system tumours, which differs depending on the age of onset and histological subtype of the tumour. High sibling risks might suggest recessive inheritance. As the high-penetrant multiplex families only accounted for about 5% of familial nervous-system tumours, most familial cases are probably caused by low-penetrance genes.

FUNDING

The Nordic Cancer Union, Deutsche Krebshilfe, the Swedish Cancer Society, and the Swedish Council for Working Life and Social Research.

Parental smoking and childhood leukemia

Childhood leukemia is the most common cancer among children, representing 31% of all cancer cases occurring in children younger than the age of 15 years in the USA. There are only few known risk factors of childhood leukemia (sex, age, race, exposure to ionizing radiation, and certain congenital diseases, such as Down syndrome and neurofibromatosis), which account for only 10% of the childhood leukemia cases. Several lines of evidence suggest that childhood leukemia may be more due to environmental rather than genetic factors, although genes may play modifying roles. Human and animal studies showed that the development of childhood leukemia is a two-step process that requires a prenatal initiating event(s) plus a postnatal promoting event(s). Despite a substantial public health effort to reduce cigarette smoking, a large proportion of the US and world population still smoke. Tobacco smoke contains at least 60 known human or animal carcinogens, with the major chemical classes being volatile hydrocarbons, aldehydes, aromatic amines, polycyclic aromatic hydrocarbons, and nitrosamines; among these chemicals, only benzene is an established leukemogen, although other chemicals in the tobacco could interact with one another in a complex way to jointly attain a significant carcinogenic effect on the development of leukemia. Although tobacco smoke is an established risk factor for adult myeloid leukemia, the studies of association between parental smoking and childhood leukemia have produced inconsistent results. The majority of the studies on maternal smoking and childhood leukemia did not find a significant positive association and some even reported an inverse association. In contrast to studies of maternal smoking, studies of paternal smoking and childhood leukemia reported more positive associations but only by less than half of the studies. Future directions to be considered for improving the study of parental smoking and childhood leukemia are: 1) consider all sources of benzene exposure in addition to smoking, including occupational exposure and traffic exhausts; 2) childhood leukemia is a heterogeneous disease and epidemiologic studies of childhood leukemia can be greatly improved by grouping childhood leukemia into more homogeneous groups by molecular techniques (e.g., structural and numerical chromosomal changes); and 3) assess gene-environment interaction. It is hoped that through the continual effort, more will be uncovered regarding the causes of childhood leukemia. In the meantime, more effort should be spent on educating the parents to quit smoking, because parental smoking is known to affect many childhood diseases (e.g., asthma, respiratory tract infection, and otitis media) that are much more prevalent than childhood leukemia.

Cancer risks among relatives of children with Hodgkin and non-Hodgkin lymphoma

A role for genetic susceptibility in the aetiology of childhood lymphomas was investigated in 454 families of children with histologically confirmed Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) from Northwest England. Cancers in parents were obtained from the UK National Health Service Central Register and in other close relatives by interview with the parents. The cancer incidence among relatives was compared with expected incidence based on cancer registry data for England. There were 197 cancers in relatives (SIR 1.0 95% CI 0.8-1.1). In families of children with HL, there was an excess of HL in the first degree relatives (SIR 5.8 95% CI 1.2-16.9). Excesses of HL diagnosed under population median age (SIR 4.1 95% CI 1.1-10.6) were seen among all relatives and relatives of children who were below the median age at diagnosis (SIR 5.5 95% CI 1.1-16.0). In families of children with NHL, there were non-significant excesses of central nervous system (CNS) tumours in the first degree relatives (SIR 2.9 95% CI 0.8-7.4) and in the second and third degree relatives (SIR 1.5). There were significant excesses of CNS tumours diagnosed under the population median age (SIR 2.8 95% CI 1.1-5.8) in all relatives. Excess CNS tumours were also seen among relatives of children below the median age at diagnosis (SIR 3.2 95% CI 1.1-7.6). In conclusion, genetic susceptibility in some families of children with lymphoma might be operating, but aetiologies in HL and NHL appear to be different. Possible interpretations of our findings, in the context of putative genetic and infectious aetiologies, are discussed.

Family cancer history and risk of brain tumors in children: results of the SEARCH international brain tumor study

OBJECTIVE

To examine whether childhood brain tumors (CBTs) are associated with a family history of brain tumors or other cancers in an international case-control study.

METHODS

Cancers in children's first- and second-degree relatives were ascertained by interview with parents of 620 children with astroglial tumors, 255 with primitive neuroectodermal tumors, 324 with other CBTs, and 2,218 controls from Australia, Canada, France, Israel, Italy, Spain, and the US. These were used with histories of neurofibromatosis or tuberous sclerosis to exclude in subanalyses children with Li-Fraumeni or other hereditary syndromes predisposing to brain tumors.

RESULTS

A first- or second-degree relative of 4% of children with astroglial tumors, 6% with PNET, 5% with other CBTs, and 5% of controls had had a brain tumor. Any potential differences were statistically non-significant, including when focusing on relatives diagnosed in childhood. In the US, where anatomical sites of relatives' other cancers were known, CBT occurrence was not associated with any other specific site. Results were not markedly altered by exclusion of children with hereditary syndromes.

CONCLUSION

Consistent with most prior studies using these methods, we observed no strong relationship between CBT occurrence and cancers in family members.

Population health and clinical data linkage: the importance of a population registry

OBJECTIVE

The Australian National Collaborative Research Infrastructure Strategy supports development of a national research capability in population health and clinical data linkage. This paper illustrates the importance of incorporating a population registry within such a system using an example provided by the Manitoba Injury Outcome Study (MIOS) that quantified the long-term burden of mortality attributable to injury in working-age adults.

METHODS

MIOS is a population-based matched cohort study that used administrative health data from Manitoba, Canada. An inception cohort of injured cases (ICD-9-CM 800-995) aged 18-64 years was identified from all Manitoba hospital admissions between 1988 and 1991. A matched non-injured comparison group was randomly selected from the total provincial population using the Manitoba Population Registry. Mortality outcomes were obtained by linking the two cohorts with the deaths data over 10 years. Mortality rate ratios (MRRs) were calculated to compare the injured and non-injured cohorts.

RESULTS

A total of 21,032 matched pairs were identified. Using the population registry, the 10-year adjusted all-cause MRR comparing injured and non-injured cohort was 1.80 (95% CI 1.65-1.98). Without the registry, the unadjusted standardised morality ratio was 2.76 (95% CI 2.52-3.02).

CONCLUSIONS

The effect of injury on mortality outcomes was over-estimated using only the injured cases, without use of the population registry. Use of the population registry enabled the selection of a matched non-injured group for comparison purposes, ensured comprehensive follow-up of almost all participants, and provided more accurate estimates of exposure time, incidence of mortality and relative risk.

Family history of cancer among children with brain tumors: a critical review

The occurrence of brain tumors in children has been anecdotally associated with an increased cancer incidence among relatives. This study rigorously reviewed the epidemiologic literature regarding family history of cancer in children with brain tumors. Six case-control and 10 cohort studies remained after applying stringent inclusion criteria. Most studies found no significant increase in cancer risk among relatives of childhood brain tumor patients. Those associations that were detected were often of borderline significance or demonstrated wide confidence intervals. There is limited evidence that a family history of cancer is more common among families of childhood brain tumor patients.

Familial history of cancer and childhood acute leukemia: a French population-based case-control study

A case-control study was conducted to investigate the role of a familial history of cancer in the etiology of childhood acute leukemia. The history of cancer in the relatives of 472 cases was compared with that of 567 population-based controls. Recruitment was frequency matched on age, sex and region. The familial history of cancer in each child's relatives was reported by the mother in response to a standardized self-administered questionnaire. A familial history of solid tumor in first or second-degree relatives was associated with an increased risk of acute lymphoblastic leukemia (odds ratio (OR)=1.6 [95% confidence interval, 1.2-2.1]), while a familial history of hematopoietic malignancies in first or second-degree relatives was associated with an increased risk of acute myeloid leukemia (OR=4.3 [1.4-13]). The ORs for the histories of cancer increased with the number of relatives with cancer (OR=1.5 [1.1-2.0] for one relative and OR=2.3 [1.3-3.8] for two relatives or more; Ptrend<0.0001). Significant associations between childhood acute leukemia and familial history of genital cancers and brain tumor were also observed (OR=2.7 [1.2-5.8] and OR=10.7 [1.3-86], respectively). This study supports the hypothesis that a familial history of cancer may play a role in the etiology of childhood acute leukemia. It also evidences some specific associations that require further investigation.

Family history of cancer in children with acute leukemia, Hodgkin's lymphoma or non-Hodgkin's lymphoma: the ESCALE study (SFCE)

The role of a family history of cancer in the etiology of childhood hematopoietic malignancies was investigated using the data from the ESCALE study. ESCALE, a population-based case-control study, was carried out in France over the period, 2003-2004. A total of 773 cases of acute leukemia (AL), 130 of Hodgkin's lymphoma (HL), 163 of non-Hodgkin's lymphoma (NHL) and 1,681 population-based controls were included. The controls were randomly selected from the French population and were frequency matched with the cases on age and gender. Cancer history in first- and second-degree relatives was reported by the mothers in a structured telephone questionnaire that was the same for the cases and controls. Odds ratios (ORs) were estimated using an unconditional regression model taking into account the stratification variables and potential confounders. A family history of cancer was associated with an increased risk of HL (OR = 1.5 [1.0-2.2]) and NHL (OR = 1.8 [1.3-2.5]), but not AL (OR = 1.0 [0.9-1.2]). The ORs were higher when at least 2 relatives had a history of cancer or when 1 case occurred before age 46 years. Only HL was significantly associated with a family history of hematopoietic malignancies (OR = 2.0 [1.0-3.8]), mainly because of a significant association with a history of HL (OR = 5.4 [1.3-22]). In conclusion, the study findings support the hypothesis of familial susceptibility to childhood lymphoma, but do not suggest familial susceptibility to childhood AL.

Ascertainment and diagnostic accuracy for hematopoietic lymphoproliferative malignancies in Sweden 1964–2003

Population-based cancer registries are widely used to provide key information about cancer incidence, survival, determinants of progression and clues about pathogenesis. To substantially expand the limited data on diagnostic accuracy and completeness for lymphoproliferative (LP) tumors in such databases, we conducted a retrospective investigation of close to 1,000 cases diagnosed during 4 decades in Sweden. We identified and reviewed medical records for 494 LP tumor patients reported to the population-based Swedish Cancer registry and 503 LP tumor patients identified from hospitals in Sweden among patients with LP tumors diagnosed during 1964-2003. The stratified samples were randomly selected from patients according to LP subtype, over 4 equal calendar periods, and among 6 selected hospitals of diverse size and from different geographic regions. We found 97.9% of reported LP tumor cases to fulfill current diagnostic criteria for having an LP tumor and observed 89.7% to have accurate LP tumor subtype. The overall completeness of non-Hodgkin lymphoma, Hodgkin lymphoma and multiple myeloma cases in the Cancer registry was 95-99% but was lower for the more indolent tumors, chronic lymphocytic leukemia (87.9%) and Waldenström's macroglobulinemia (68.1%). We observed increased overall under-ascertainment for patients diagnosed above age 80 (27%) and among individuals diagnosed before 1973 (12%). In conclusion the diagnostic accuracy and completeness for classically defined LP tumor entities in the Swedish Cancer registry is high. However, we found under-ascertainment of patients with indolent LP tumors, particularly among patients diagnosed at older ages, with early-stage disease and diagnosed in earlier years.

Association of childhood acute lymphoblastic leukaemia with cancers in family members

Children whose twins have had leukaemia have a higher risk of contracting acute lymphoblastic leukaemia (ALL), confirming a prenatal origin of the disease. This association was not true when considering other types of affected first-degree relatives. Children whose fathers were diagnosed with testicular cancer have a higher risk of ALL.

Increased risk of cancer among siblings of long-term childhood cancer survivors: a report from the childhood cancer survivor study

We determined risk of cancer among first-degree relatives of 5-year survivors of childhood leukemia, lymphoma, central nervous system tumors, sarcomas, Wilms' tumor, and neuroblastoma. Subjects were 13,703 participants in the Childhood Cancer Survivor Study. Family history was collected on 56,759 first-degree relatives using a self-reported questionnaire. Incidence was compared with age- and sex-specific rates using the U.S. Surveillance, Epidemiology and End Results program. Siblings of the survivors had an increased risk of cancer [standardized incidence ratio (SIR), 1.5; 95% confidence interval (95% CI), 1.35-1.7]. Risk was elevated for siblings of probands of leukemia (SIR, 1.3; 95% CI, 1.0-1.6), Hodgkin's disease (SIR, 1.5; 95% CI, 1.2-1.9), non-Hodgkin's lymphoma (SIR, 1.8; 95% CI, 1.3-2.5), Wilms' tumor (SIR, 1.9; 95% CI, 1.2-3.2), soft tissue sarcoma (SIR, 1.5; 95% CI, 1.0-2.2), and bone tumors (SIR, 1.6; 95% CI, 1.2-2.2). Cancer risk was elevated in siblings (SIR, 2.4; 95% CI, 1.5-3.7) and offspring (SIR, 15.0; 95% CI, 5.3-42.9) of probands with second malignant neoplasms (SMN) compared with relatives of probands without SMNs. Siblings of probands with leukemia, Hodgkin's disease, neuroblastoma, and Wilms' tumor had elevated risks for the same malignancies. Parents had no increased risk (fathers' SIR, 0.7; 95% CI, 0.7-0.8; mothers' SIR, 0.9; 95% CI, 0.9-1.0). Seventy percent of siblings' cancers developed in adulthood. These findings suggest that familial cancer syndromes may be revealed as this cohort and family members age and with accrual of more offspring and subjects with SMNs.

Socioeconomic status and risk of childhood leukaemia in Denmark

AIMS

The aim of this study was to assess the influence of socioeconomic status on the risk of childhood leukaemia.

METHODS

A matched case-control design was used. The study population comprised all children (0-14 years old) born and reported to the Danish Cancer Registry between 1976 and 1991 for a diagnosis of leukaemia (n=377). Controls were selected from the Central Population Registry and matched by sex, age, and time of birth. Each child was assigned three categories of socioeconomic status, one corresponding to the annual average income in the municipality of residence at the time of birth, another corresponding to that at the time of diagnosis, and, finally, each family was assigned one of five social classes by use of the job titles of the parents. Conditional logistic regression was used to estimate the effect of socioeconomic status on the risk of childhood leukaemia.

RESULTS

Children born in low-income municipalities had a significantly increased risk of leukaemia (RR=2.71; 95% CI=1.41-5.21; p=0.003), which was higher among those who received their diagnosis before age five (RR=3.43; 95% CI=1.52-7.74; p=0.003). Neither individual social class nor the socioeconomic status of the residential area at the time of diagnosis was convincingly associated with the risk of childhood leukaemia.

CONCLUSIONS

The results suggest that socioeconomic factors associated with community characteristics rather than individual lifestyle are related to the risk of childhood leukaemia and that these factors act early in life.

Familial risk of lymphoproliferative tumors in families of patients with chronic lymphocytic leukemia: results from the Swedish Family-Cancer Database

The importance of genetic factors in etiology of chronic lymphocytic leukemia (CLL) is suggested by family and population studies. However, the spectrum of malignancies sharing common genetic factors with CLL and the effects of sex and age on familial risk are unknown. We used the Swedish Family-Cancer Database to test for increased familial risks of CLL and other lymphoproliferative tumors. Cancer diagnoses from 1958 to 1998 were assessed in 14 336 first-degree relatives of 5918 CLL cases and in 28 876 first-degree relatives of 11 778 controls. Cancer risks in relatives of cases were compared with those in relatives of controls using marginal survival models. Relatives of cases were at significantly increased risk for CLL (relative risk [RR] = 7.52; 95% confidence interval [CI], 3.63-15.56), for non-Hodgkin lymphoma (RR = 1.45; 95% CI, 0.98-2.16), and for Hodgkin lymphoma (RR = 2.35; 95% CI, 1.08-5.08). CLL risks were similar in parents, siblings, and offspring of cases, in male and female relatives, and were not affected by the case's age at diagnosis. Anticipation was not significant when analyzed using life table methods. We conclude that the familial component of CLL is shared with other lymphoproliferative malignances, suggesting common genetic pathways. However, because clinically diagnosed CLL is uncommon, absolute excess risk to relatives is small.

Epidemiology and genetics of childhood cancer

Childhood cancer is rare everywhere in the world, with age-standardized annual incidence usually between 70 and 160 per million at age 0-14 years. Greater variation is seen between populations for some specific tumour types. Some of the largest variations are geographical and are attributable to environmental factors, whereas variation mainly on ethnic lines seems likely to be a marker of genetic predisposition. A wide range of familial and genetic syndromes is associated with an increased risk of childhood cancer. Virtually all the excess risk of cancer among first-degree relatives of children with cancer can be accounted for by known hereditary syndromes. Studies of weak predisposition and gene-environment interaction have so far shown limited consistency. There are very few established environmental or exogenous risk factors and most of these are infective agents. Many putative risk factors can hardly ever be investigated epidemiologically except by interview or questionnaire studies. Some recent examples illustrate the continuing problems of participation bias and recall bias.