Analysis of risk factors in a cluster of childhood acute lymphoblastic leukemia

Epidemiology of acute lymphoblastic leukaemia in Sardinia, Italy: Age, sex, and environmental correlates

Using a database of 1974-2003 incident cases of haematological malignancies, we explored the time trend, geographic spread and socio-economic and environmental correlates of ALL incidence in Sardinia, Italy, by sex and age. The age- and sex-standardized (World population) ALL incidence rate was 2.0 per 100,000 (95% CI 1.8 - 2.1) and showed variable trend patterns by sex and age. In the total population, ALL incidence showed an annual per cent change of -1.4% (95% CI -0.59 - -3.34) over the study period, with a knot separating a downward slope in 1974-1996 from an increase in 1996-2003. ALL incidence replicated such pattern in women but not men, whose incidence did not substantially vary over the study period (APC = -2.57%, 95% CI -5.45 - 0.26). Among women, the spatial analysis suggested a clustering of ALL in the southwestern part of the region, whilst only a commune had a high posterior probability of a high ALL incidence among men. Three unrelated communes showed a high posterior probability of ALL at age ≤ 24; only the most populated urban centre showed excess cases at age ≥ 25 years. There was no correlation between the geographic spread of ALL at ages ≤ 24 and ≥ 25 years (p = 0.082). Urban residence was a risk factor for the younger age group. Residences near industrial settlements and in the most populated urban centre were risk factors for subjects aged ≥ 25 years. Our findings suggest age-related differences in ALL aetiology.

Haemolymphatic cancer among children in Sardinia, Italy: 1974-2003 incidence

OBJECTIVES

To explore the time trend and geographical distribution of childhood leukaemia incidence over the territory of the Italian region of Sardinia.

SETTING

All hospitals departments, diagnostic centres and social security agencies in Sardinia were regularly screened in 1974-2003 to identify, register and review the diagnoses of incident cases of haematological malignancies (HM).

PARTICIPANTS

The whole child population aged 0-14 resident in Sardinia.

PRIMARY AND SECONDARY OUTCOME MEASURES

Incidence and time trend of childhood HM and childhood acute lymphoblastic leukaemia (ALL) over the study period, and use of Bayesian methods to plot the probability of areas with excess incidence on the regional map.

RESULTS

Overall, 675 HM cases, including 378 ALL cases, occurred among children aged 0-14 years resident in Sardinia in 1974-2003, with an incidence rate of 6.97×10^-5 (95% CI 6.47 to 7.51) and 3.85×10^-5 (95% CI 3.48 to 4.26), respectively. Incidence of HM and ALL showed an upward trend along the study period especially among females. Three communes out of the 356 existing in 1974, namely Ittiri, Villa San Pietro and Carbonia, stand out as areas with excess incidence of HM and ALL in particular and another, Carloforte, for ALL only.

CONCLUSIONS

Our results might serve as convincing arguments for extending the coverage of routine cancer registration over the whole Sardinian population, while prompting further research on the genetic and environmental determinants in the areas at risk.

Tobacco smoke exposure and the risk of childhood acute lymphoblastic leukemia and acute myeloid leukemia: A meta-analysis

OBJECTIVE

Tobacco smoke contains carcinogens known to damage somatic and germ cells. In this study, we investigated the effect of tobacco smoking on the risk of childhood acute lymphoblastic leukemia (ALL) and myeloid leukemia (AML).

METHODS

Information about tobacco smoking exposures of the mother before, during, and after pregnancy was collected via PubMed, Embase, and Web of Science databases through November 5, 2018. We performed to evaluate the association between smoking exposure and the risk of childhood ALL and AML. Study selection, data abstraction, and quality assessment were performed by 2 independent reviewers. Random effects models were used to obtain summary odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Nineteen case-control studies of childhood leukemia (age < 15 years) conducted in 9 countries from 1974 to 2018. Maternal smoking exposures did not a significant association with childhood ALL (OR = 1.004, 95% CI 0.953-1.058, P = .881) and AML (OR = 0.92, 95% CI 0.815-1.038, P = .177) during exposure time windows. However, there was an association with paternal smoking and ALL (OR = 1.15, 95% CI 1.038-1.275, P = .007). Paternal smoking in AML showed there was no association with smoking exposures and childhood AML (OR = 1.133, 95% CI 0.943-1.362, P = .181). Next, maternal daily cigarettes consumption showed no associations with ALL (OR = 1.08, 95% CI 1.000-1.168, P = .051) during pregnancy. No association with maternal daily smoking and AML (OR = 0.909, 95% CI 0.682-1.211, P = .514). Paternal daily cigarettes consumption was associated with increased risks of childhood ALL (OR = 1.200, 95% CI 1.112-1.302, P = .000). The higher consumption of paternal smoking (more than 10 per day) was significantly related to childhood ALL. Paternal daily smoking consumption also was related to AML (OR = 1.242, 95% CI 1.031-1.496, P = .022).

CONCLUSION

Maternal smoking before, during, or after pregnancy was not associated with childhood ALL or AML. However, paternal smoking was related to a significantly elevated risk of childhood ALL during pregnancy, but not for AML. Maternal daily smoking consumption was not associated with ALL or AML during pregnancy. The higher consumption of paternal smoking were, the higher the risk of childhood ALL or AML.

Maternal fetal loss history and increased acute leukemia subtype risk in subsequent offspring: a systematic review and meta-analysis

PURPOSE

History of fetal loss including miscarriage and stillbirth has been inconsistently associated with childhood (0-14 years) leukemia in subsequent offspring. A quantitative synthesis of the inconclusive literature by leukemia subtype was therefore conducted.

METHODS

Eligible studies (N = 32) were identified through the screening of over 3500 publications. Random-effects meta-analyses were conducted on the association of miscarriage/stillbirth history with overall (AL; 18,868 cases/35,685 controls), acute lymphoblastic (ALL; 16,150 cases/38,655 controls), and myeloid (AML; 3042 cases/32,997 controls) leukemia. Sensitivity and subgroup analyses by age and ALL subtype, as well as meta-regression were undertaken.

RESULTS

Fetal loss history was associated with increased AL risk [Odds Ratio (OR) 1.10, 95% Confidence Intervals (CI) 1.04-1.18]. The positive association was seen for ALL (OR 1.12, 95%CI 1.05-1.19) and for AML (OR 1.13, 95%CI 0.91-1.41); for the latter the OR increased in sensitivity analyses. Notably, stillbirth history was significantly linked to ALL risk (OR 1.33, 95%CI 1.02-1.74), but not AML. By contrast, the association of ALL and AML with previous miscarriage reached marginal significance. The association of miscarriage history was strongest in infant ALL (OR 2.34, 95%CI 1.19-4.60).

CONCLUSIONS

In this meta-analysis involving >50,000 children, we found noteworthy associations by indices of fetal loss, age at diagnosis, and leukemia type; namely, of stillbirth with ALL and miscarriage history with infant ALL. Elucidation of plausible underlying mechanisms may provide insight into leukemia pathogenesis and indicate monitoring interventions prior to and during pregnancy.

Reported associations between asthma and acute lymphoblastic leukemia: insights from a hybrid simulation study

Numerous studies have reported a protective association between asthma and acute lymphoblastic leukemia (ALL), but the causal structure of this association remains unclear. We present a hybrid simulation to examine the compatibility of this association with uncontrolled confounding by infection or another unmeasured factor. We generated a synthetic cohort using inputs on the interrelations of asthma, ALL, infections, and other suggested risk factors from the literature and the Danish National Birth Cohort. We computed odds ratios (ORs) between asthma and ALL in the synthetic cohort with and without adjustment for infections and other (including unmeasured) confounders. Only if infection was an extremely strong risk factor for asthma (OR of 10) and an extremely strong protective factor against ALL (OR of 0.1) was the asthma-ALL association compatible with the literature (OR of 0.78). Similarly, strong uncontrolled confounding by an unmeasured factor could downwardly bias the asthma-ALL association, but not enough to replicate findings in the literature. This investigation illustrates that the reported protective association between asthma and ALL is unlikely to be entirely due to uncontrolled confounding by infections or an unmeasured confounder alone. Simulation can be used to advance our understanding of risk factors for rare outcomes as demonstrated by this study.

Parental, In Utero, and Early-Life Exposure to Benzene and the Risk of Childhood Leukemia: A Meta-Analysis

Benzene is an established cause of adult leukemia, but whether it is associated with childhood leukemia remains unclear. We conducted a meta-analysis in which we reviewed the epidemiologic literature on this topic and explored causal inference, bias, and heterogeneity. The exposure metrics that we evaluated included occupational and household use of benzenes and solvents, traffic density, and traffic-related air pollution. For studies of occupational and household product exposure published from 1987 to 2014, the summary relative risk for childhood leukemia was 1.96 (95% confidence interval (CI): 1.53, 2.52; n = 20). In these studies, the summary relative risk was higher for acute myeloid leukemia (summary relative risk (sRR) = 2.34, 95% CI: 1.72, 3.18; n = 6) than for acute lymphoblastic leukemia (sRR = 1.57; 95% CI: 1.21, 2.05; n = 14). The summary relative risk was higher for maternal versus paternal exposure, in studies that assessed benzene versus all solvents, and in studies of gestational exposure. In studies of traffic density or traffic-related air pollution published from 1999 to 2014, the summary relative risk was 1.48 (95% CI: 1.10, 1.99; n = 12); it was higher for acute myeloid leukemia (sRR = 2.07; 95% CI: 1.34, 3.20) than for acute lymphoblastic leukemia (sRR = 1.49; 95% CI: 1.07, 2.08) and in studies that involved detailed models of traffic pollution (sRR = 1.70; 95% CI: 1.16, 2.49). Overall, we identified evidence of associations between childhood leukemia and several different potential metrics of benzene exposure.

Maternal smoking during pregnancy and risk for childhood leukemia: a nationwide case-control study in Greece and meta-analysis

BACKGROUND

Maternal smoking during pregnancy has been often implicated in the development of childhood leukemia with ambiguous results. Hence, we conducted a meta-analysis aiming to summarize current evidence and quantify any tentative impact.

PROCEDURE

We retrieved one cohort (553 leukemias compared to 1,440,542 children), 20 case-control studies and also analyzed the updated Greek case-control dataset with unpublished data, yielding in total 11,092 cases and 25,221 controls.

RESULTS

Odds ratios reported in the studies included ranged from 0.70 to 2.20 for acute lymphocytic (ALL) and from 0.60 to 2.17 for acute myelocytic leukemia (AML). The combined effect regarding the association of maternal smoking (any vs. no) and leukemia risk was 1.03 for ALL (95% CI = 0.95-1.12, random effects model) and 0.99 for AML (95% CI = 0.90-1.09, fixed effects model). The results remained unchanged when sensitivity analyses were undertaken of studies reporting same maternal smoking periods, those focusing only on childhood leukemia deaths or investigations which did not clearly define AML subtype.

CONCLUSIONS

The findings of the meta-analysis challenge the limits of traditional epidemiology to provide sound inferences when point estimates of constituent studies range around the null. In particular, this study provides no support to a hypothesis linking maternal smoking during pregnancy with subsequent development of main childhood leukemia subtypes. Further investigations employing molecular and genetic epidemiology, however, might be needed in the hope to reveal even minimal risks pertaining individuals with specific susceptibility to tobacco compounds who sustain high environmental exposures prenatally or postnatally.

Paternal smoking and risk of childhood acute lymphoblastic leukemia: systematic review and meta-analysis

Objective. To investigate the association between paternal smoking and childhood acute lymphoblastic leukemia (ALL). Method. We identified 18 published epidemiologic studies that reported data on both paternal smoking and childhood ALL risk. We performed a meta-analysis and analyzed dose-response relationships on ALL risk for smoking during preconception, during pregnancy, after birth, and ever smoking. Results. The summary odds ratio (OR) of childhood ALL associated with paternal smoking was 1.11 (95% Confidence Interval (CI): 1.05-1.18, I(2) = 18%) during any time period, 1.25 (95% CI: 1.08-1.46, I(2) = 53%) preconception; 1.24 (95% CI: 1.07-1.43, I(2) = 54%) during pregnancy, and 1.24 (95% CI: 0.96-1.60, I(2) = 64%) after birth, with a dose-response relationship between childhood ALL and paternal smoking preconception or after birth. Conclusion. The evidence supports a positive association between childhood ALL and paternal ever smoking and at each exposure time period examined. Future epidemiologic studies should assess paternal smoking during well-defined exposure windows and should include biomarkers to assess smoking exposure and toxicological mechanisms.

Alcohol, signaling, and ECM turnover

Alcohol is recognized as a direct hepatotoxin, but the precise molecular pathways that are important for the initiation and progression of alcohol-induced tissue injury are not completely understood. The current understanding of alcohol toxicity to organs suggests that alcohol initiates injury by generation of oxidative and nonoxidative ethanol metabolites and via translocation of gut-derived endotoxin. These processes lead to cellular injury and stimulation of the inflammatory responses mediated through a variety of molecules. With continuing alcohol abuse, the injury progresses through impairment of tissue regeneration and extracellular matrix (ECM) turnover, leading to fibrogenesis and cirrhosis. Several cell types are involved in this process, the predominant being stellate cells, macrophages, and parenchymal cells. In response to alcohol, growth factors and cytokines activate many signaling cascades that regulate fibrogenesis. This mini-review brings together research focusing on the underlying mechanisms of alcohol-mediated injury in a number of organs. It highlights the various processes and molecules that are likely involved in inflammation, immune modulation, susceptibility to infection, ECM turnover and fibrogenesis in the liver, pancreas, and lung triggered by alcohol abuse.

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.

Descriptive survey about causes of illness given by the parents of children with cancer

BACKGROUND

When a doctor diagnoses a child's illness as cancer, parents very often react by creating wrong and unrealistic theories about the origins of their child's illness which in turn generates self-blame in the parents, who take responsibility for the disease.

OBJECTIVE

To find what are the parents' beliefs about the origins of their children's illness.

DESIGN

Descriptive study.

SAMPLE

Seventy-two couples of parents whose children with cancer are under treatment in the haemato-oncology paediatric ward of the Padova hospital. They have been collected by a no probabilistic method of sampling.

METHODS

A questionnaire was used, based on current literature, which investigates the beliefs of the parents as to what are the causes of illness, whether the parents research information about the illness and the origins of cancer and what are the information sources they use in order to establish if there is a connection between these factors.

RESULTS

Eighty-seven percent of the sample group thinks that there is a specific origin of their child's illness: 27% believes the cause is environmental pollution, 26% believes it is due to radiation emissions, 26% believes it is due to genetic factors and 8% believes it is due to other causes. Eighty six percent and 70% of the sample search for information about the illness and its causes; 64% of the parents state that the first meeting with the medical staff, in which the illness is explained and they are informed that there are no known causes that produce it, does not clarify their doubts. The sources more often used to search for more information and explanations are the physicians in the ward, internet and medical books.

CONCLUSIONS

This survey confirms the importance of an "advocacy" role of the nurse in educating the caregiver and the need to create instruments which guide the parents in the informative process and the research for good information. Nurses need to be cognizant that their care is crucial not just for the child, but for the entire family.

Participative risk communication in an industrial village in Sardinia

OBJECTIVE

In Italy the law on industrial risk has emphasised the necessity of building a local information process to answer people's questions on safety and provide greater community participation in risk management. The aim of this research is to analyse the local population's ideas and expectations of a participatory approach in risk management in order to design a risk communication programme based on health promotion principles.

DESIGN, SETTING AND PARTICIPANTS

The study was carry out in Portoscuso (Italy), an industrial district. A questionnaire was administrated through home interviews to 147 citizens.

MAIN RESULTS

Six risk management styles were identified on the basis of citizens' trust in the different stakeholders. Additional parameters (importance of information, organisations they would trust to get information on industrial risks, preferred risk communication methodologies) were analysed according to the management styles.

CONCLUSIONS

On the basis of these elements, a multi-approach strategy could be proposed. Each management style can have different roles. A programme of public forums could involve citizens with an interactive approach, interactive courses could involve citizens with a semi-participative approach, and leaflets and booklets could inform citizens oriented towards unidirectional communication. The participative process should always be open to new contributions from citizens who are not directly involved, and should allow for flexibility in the form and nature of partnership, as well as the details of implementation.

Parental alcohol consumption and childhood cancers: a review

The etiology of childhood cancers remains generally unknown. Given that the metabolites of alcohol are likely carcinogens and that leukemia, the most frequent childhood cancer, can arise in utero, the study of alcohol consumption as a potential risk factor for the development of childhood cancer is justified. This article summarizes the epidemiological evidence on the association between parental exposure to alcohol and the risk of childhood cancers. To do this, a thorough search of the literature from 1960 to 2003 using the PubMed database was carried out. It yielded 33 case-control studies published between 1982 and 2003, including 13 studies that considered paternal exposure in the preconceptional period. In 10 of the 33 studies at least 1 statistically significant risk increase was reported in relation with parental alcohol consumption; in 7 of these studies the increase was related to maternal consumption, whereas in 3 studies, it was related to paternal consumption. The cancers most often found associated with parental drinking were leukemia, brain tumors, and neuroblastoma. A few studies also reported a protective effect with maternal exposure at modest levels. Inconsistencies in the results and the low risks reported do not suggest an association between childhood cancer and parental consumption of alcohol. However, before reaching any definitive conclusions, methodological issues need to be addressed in future studies, as well as the role of genetic susceptibility. Moreover, subtypes of specific cancers need to be studied separately.

Parental Occupational Exposure and the Risk of Acute Lymphoblastic Leukemia in Offspring in Israel

OBJECTIVE

Parental employment in occupations that have potential exposures to organic solvents or pesticides could be associated with the risk of childhood acute lymphoblastic leukemia (ALL) in their offspring.

METHODS

We explored this hypothesis by studying the association with respect to exposure time windows. Our case-control study included 224 children, 112 diagnosed with ALL and 112 matched controls.

RESULTS

A significantly higher odds ratio (OR) was found between childhood ALL and reported parental occupational exposures. Analysis of exposures of both parents by exposure time windows revealed significant OR during the preconception and postnatal periods separately.

CONCLUSIONS

The results provide support to the association between parental occupational exposures and ALL in their children. These results should be interpreted cautiously because of the small numbers, biases characterizing case-control studies, and the use of hospital-based controls.

Socioeconomic status and childhood leukaemia: a review

BACKGROUND

A long-held view links higher socioeconomic status (SES) to higher rates of childhood leukaemia. Some recent studies exhibit associations in the opposite direction.

METHODS

We reviewed journal literature through August 2002 for associations between childhood leukaemia and socioeconomic measures. We determined the direction of each association and its P-value. We described the results with regard to study design, calendar period, geographic locale, and level of the socioeconomic measures (individual or ecological). For measures with sufficient number of results, we computed summary P-values across studies.

RESULTS

Case-control studies conducted in North America since 1980 have involved subject interviews or self-administered questionnaires and have consistently reported inverse (negative) associations of childhood leukaemia with individual-level measures of family income, mother's education, and father's education. In contrast, associations have been consistently positive with father's occupational class in record-based case-control studies and with average occupational class in ecological studies.

CONCLUSIONS

Connections of SES measures to childhood leukaemia are likely to vary with place and time. Validation studies are needed to estimate SES-related selection and participation in case-control studies. Because different socioeconomic measures (such as income and education) and individual-level and ecological-level measures may represent different risk factors, we advise researchers to report these measures separately rather than in summary indices of social class.

Maternal Diet and Acute Lymphoblastic Leukemia in Young Children

Because leukemia clone-specific chromosomal abnormalities are present at birth in children who later develop leukemia, it has been hypothesized that maternal factors, including nutrition during pregnancy, might affect the risk of acute lymphoblastic leukemia (ALL) among young children. We have evaluated this hypothesis in a nationwide case-control study of ALL among children ages 12 to 59 months in Greece. Children (n = 131) with ALL were gender and age matched to control children (n = 131) hospitalized for minor conditions between 1999 and 2003. The mothers of the children were interviewed in person by trained interviewers who used an extensive food frequency questionnaire addressing diet during the index pregnancy. The analysis was done by modeling the data through conditional logistic regression, also controlling for total energy intake and possible confounding factors. Odds ratios (OR) and 95% confidence intervals (95% CI) were expressed per quintile increase of maternal intake during pregnancy of the specified food group. The risk of ALL in the offspring was lower with increased maternal intake of fruits (OR, 0.72; 95% CI, 0.57-0.91), vegetables (OR, 0.76; 95% CI, 0.60-0.95), and fish and seafood (OR, 0.72; 95% CI, 0.59-0.89) and higher with increased maternal intake of sugars and syrups (OR, 1.32; 95% CI, 1.05-1.67) and meat and meat products (OR, 1.25; 95% CI, 1.00-1.57). Children of women who tend to consume during their pregnancies what is currently considered to be a healthy diet maybe at lower risk of ALL.

Risk of childhood germ cell tumors in association with parental smoking and drinking

BACKGROUND

The etiology of childhood germ cell tumors (GCT) is not well understood. The Children's Oncology Group conducted the largest case-control study of childhood GCT to investigate whether parental exposures to smoking and alcohol contributed to the disease.

METHODS

Cases included 274 children with GCT diagnosed between January 1, 1993 and December 31, 2001 who were age <15 years. Controls (n=421) were selected by random digit dialing and were frequency matched based on gender, age (+/-1 year), and geographic area. Exposure information was collected from subjects' parents using independent telephone interviews and self-administrated questionnaires.

RESULTS

No association was found between parental smoking or drinking alcohol and risk of childhood GCT (for smoking: odds ratio [OR]=1.0, 95% confidence interval [95% CI], 0.8-1.3 and OR = 1.2, 95% CI, 0.9-1.5, for mothers and fathers, respectively; for drinking: OR=0.9, 95% CI, 0.7-1.2 and OR=1.0, 95% CI, 0.8-1.3, for mothers and fathers, respectively). No significant trend was observed for length of maternal exposure to passive smoking during the index pregnancy and GCT risk (for total subject: P=0.77; boys: P=0.52; girls: P=0.93).

CONCLUSIONS

The authors found no evidence that childhood GCT was related to prenatal exposure to parental cigarette smoking, alcohol drinking, and maternal passive smoking.

Use of medication during pregnancy and risk of childhood leukemia (Canada)

OBJECTIVE

To examine risk of childhood acute lymphoblastic leukemia (ALL) associated with maternal use of medications during pregnancy; in particular medications known or suspected to be teratogenic.

METHODS

Seven hundred and eighty nine children (< 15 years old) diagnosed with ALL in the province of Quebec between 1980 and 2000 were recruited for study. A similar number of population based controls matched to cases (1:1) by sex and age were chosen from family allowance or health insurance files. Information was gathered via telephone interview with the subjects' parents. Data were analyzed using conditional logistic regression.

RESULTS

Risk of childhood ALL was significantly increased in the offspring of mothers who reported using any medication (adjusted odds ratio (OR(adj)) = 1.3, 95% CI = 1.0-1.6) or any teratogenic medication (OR(adj) = 1.4, 95% CI = 1.1-1.9) during pregnancy. Among specific medication categories, only central nervous system depressants were associated with a significantly increased risk, although elevated odd ratios were found for anti-epileptics, immunosuppressants, oral contraceptives, and illicit drugs. Risk associated with use of teratogenic medications was higher with increased dose and in children diagnosed before two years of age.

CONCLUSION

A modest increase in risk of ALL was found among children of mothers who used medication during pregnancy.

Household solvent exposures and childhood acute lymphoblastic leukemia

OBJECTIVES

This study explored the risk of childhood acute lymphoblastic leukemia (ALL) associated with participation by household members in hobbies or other home projects involving organic solvents.

METHODS

Participants in this case-control study were 640 subjects with ALL and 640 matched controls.

RESULTS

Childhood ALL was associated with frequent (> 4 times/month) exposure to model building (odds ratio [OR] = 1.9; 95% confidence interval [95% CI] = 0.7, 5.8) and artwork using solvents (OR = 4.1; 95% CI = 1.1, 15.1). We also found elevated risk (OR = 1.7; 95% CI = 1.1, 2.7) among children whose mothers lived in homes painted extensively (> 4 rooms) in the year before the children's birth.

CONCLUSIONS

In this exploratory study, substantial participation by household members in some common household activities that involve organic solvents was associated with elevated risks of childhood ALL.

Clusters and clustering of childhood cancer: a review

Methodological considerations in the study of clusters and clustering of childhood cancer are reviewed briefly. A selection of 11 studies of individual clusters of childhood leukaemia which are either particularly notable or recent and have been reported in peer review journals is then considered. Focus is placed on sources of alerts, descriptive studies, field-work studies, conclusions and communication management. Some of these studies are probably essential but they are unlikely to yield firm conclusions; studies of large data sets are recommended. No causal factor has been identified which can explain a single cluster of childhood leukaemia.

The risk profile of childhood leukaemia in Greece: a nationwide case-control study

The risk profile of childhood leukaemia in Greece was studied through a case-control investigation that included all 153 incident cases of the disease, ascertained throughout the country during 1993 and 1994, and two hospital controls for every case matched for gender, age and place of residence. The data were analysed using conditional logistic regression and the associations are expressed in terms of adjusted odds ratios (OR) and their 95% confidence intervals. Cases were born to mothers of a higher standard education, the OR for an increment of four schooling years being 1.48 (1.17-1.87) and had higher birth weight, the OR for an increment of 500g being 1.36 (1.04-1.77). Pet ownership and birth after a pregnancy with anaemia were associated with increased risk, the ORs being 2.18 (1.14-4.16) and 2.60 (1.39-4.86) respectively. From the frequency analyses, indicative inverse associations were found with birth order, household crowding and previous hospitalization with allergic diseases, whereas indicative positive associations were found with diabetes mellitus during pregnancy and with neonatal jaundice. Substantial or significant elevations were not found with respect to maternal smoking and coffee drinking during pregnancy, diagnostic radiography and ultrasonographic examinations or blood transfusions. A significant inverse association with maternal consumption of alcohol could be due to multiple comparisons, but a detrimental effect can probably be excluded. A non-significant positive association with total shots of viral vaccinations and a weak non-significant inverse association with breast feeding were also found. We interpret the findings of this study as being compatible with acute childhood leukaemia being linked with delayed development of herd immunity to fairly common infectious agents, in conjunction with accelerated perinatal and early post-natal growth.