Risk factors for childhood leukaemia. Discussion and summary

The Krümmel (Germany) Childhood Leukaemia Cluster: a review and update

The debate surrounding possible adverse health effects from the civil use of nuclear power under normal operating conditions has been on-going since its introduction. It was particularly intensified by the detection of three leukaemia clusters near nuclear installations, i.e. near the reprocessing plants in Sellafield and Dounreay, UK, and near the Krümmel nuclear power plant, Germany, the last of which commenced between 1990 and 1991 and was first described in 1992; it continued until 2003, and an elevated risk up to 2005 has been reported in the literature. A number of expert commissions and working groups were set up by the governments of the German federal states of Lower Saxony and Schleswig-Holstein to investigate the possible causes of the cluster. An overview of the many risk factors that were investigated as a possible explanation of the Krümmel cluster is given here, focussing on radiation, but also including other risk factors. Further, results from related epidemiological and cytogenetic studies are described. In summary, the cause of the occurrence of the Krümmel cluster has to be considered as unknown. Further research on the causes of childhood leukaemia is needed, focussing on epigenetics and on gene-environment interaction. An update of the leukaemia incidence around the Krümmel site shows that the incidence rates are now comparable to the average rate in Germany.

Background gamma radiation and childhood cancer in Germany: an ecological study

The relationship of low-dose background gamma radiation and childhood leukaemia was investigated in a number of studies. Results from these studies are inconclusive. Therefore, in the present study 25 years of German childhood cancer data were analyzed using interpolated background annual gamma dose rate per community in an ecological study. The main question was leukaemia; as exploratory questions we investigate central nervous system (CNS) tumours, thyroid carcinomas and diagnoses less likely to be related to radiation. A Poisson regression model was applied and a fractional polynomial model building procedure. As the main sensitivity analysis a community deprivation index was included as a potential confounder. It was found that outdoor background gamma annual dose rates in Germany range roughly from 0.5-1.5 mSv/a with an average of 0.817 mSv/a. No association of annual ambient gamma dose rates with leukaemia incidence was found. Amongst the exploratory analyses, a strong association was found with CNS tumour incidence [rate ratio for 1.5 vs 0.5 mSv/a: 1.35; 95% confidence interval (1.17, 1.57)]. The community level deprivation index was not a confounder. It is concluded that the present study did not confirm an association of annual outdoor ambient gamma dose rate and childhood leukaemia, corresponding to some studies and contrasting others. An association with CNS incidence was found in the exploratory analyses. As this is an ecological study no causal interpretation is possible.

Incidence of common preleukemic gene fusions in umbilical cord blood in Slovak population

The first event in origination of many childhood leukemias is likely the presence of preleukemic clone (transformed hematopoietic stem/progenitor cells with preleukemic gene fusions (PGF)) in newborn. Thus, the screening of umbilical cord blood (UCB) for PGF may be of high importance for developing strategies for childhood leukemia prevention and treatment. However, the data on incidence of PGF in UCB are contradictive. We have compared multiplex polymerase chain reaction (PCR) and real-time quantitative PCR (RT qPCR) in neonates from Slovak National Birth Cohort. According to multiplex PCR, all 135 screened samples were negative for the most frequent PGF of B-lineage acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). To explore the prevalence of prognostically important TEL-AML1, MLL-AF4 and BCR-ABL (p190), 200 UCB were screened using RT qPCR. The initial screening showed an unexpectedly high incidence of studied PGF. The validation of selected samples in two laboratories confirmed approximately ¼ of UCB positive, resulting in ∼4% incidence of TEL-AML1, ∼6.25% incidence of BCR-ABL1 p190, and ∼0.75% frequency of MLL-AF4. In most cases, the PGF presented at very low level, about 1–5 copies per 10⁵ cells. We hypothesize that low PGF numbers reflect their relatively late origin and are likely to be eliminated in further development while higher number of PGF reflects earlier origination and may represent higher risk for leukemia.

Trends in cancer mortality in China: an update

BACKGROUND

Cancer deaths of China with the world population nearly a quarter will have a severe impact on global cancer trend and burden. The study aims to provide a comprehensive overview of long-term trends in cancer mortality in China.

MATERIALS AND METHODS

We used joinpoint analysis to detect changes in trends and generalized additive models to study birth cohort effect of risk factors between 1987 and 2009.

RESULTS

Mortality of all cancers declined steadily in urban areas, but not in rural areas. Decreasing mortality from cancers of the stomach, esophagus, nasopharynx, and cervix uteri was observed, while lung and female breast cancer mortality increased. Mortality from leukemia remained relatively stable, and cancer of liver, colorectal, and bladder had different trends between the rural and urban areas. Generational risks peaked in the cohorts born around 1925-1930 and tended to decline in successive cohorts for most cancers except for leukemia, whose relative risks were rising in the very recent cohorts.

CONCLUSION

The observed trends primarily reflect dramatic changes in socioeconomic development and lifestyle in China over the past two decades, and mortality from cancers of lung and female breast still represents a major public health priority for the government.

Maternal use of antibiotics and cancer in the offspring: results of a case-control study in Germany

OBJECTIVE

As previous results were inconsistent, we assessed the association between maternal use of antibiotics during pregnancy or 3 months before conception and childhood cancer in the offspring in a large case-control study in Germany.

METHODS

This population-based study on potential risk factors for childhood cancer was conducted by the German Childhood Cancer Registry (GCCR) and included a total of 1,867 registered cancer cases aged 0-14, diagnosed between October 1992 and September 1994. A total of 2,057 controls were randomly drawn from population registries, matched by age, gender, and region. Conditional logistic regression models for frequency-matched datasets were used to estimate odds ratios (OR) with 95% confidence intervals (95% CI).

RESULTS

Positive statistically significant associations with self-reported maternal antibiotic use were observed for acute lymphoid leukemia (based on 59 mothers exposed to antibiotics, OR = 1.47; 95% CI: 1.06-2.04), acute myeloid leukemia (18 exposed, OR = 3.21; 95% CI: 1.83-5.62), and Burkitt lymphoma (three exposed, OR = 5.89; 95% CI: 1.47-23.69), but not other cancer types.

CONCLUSIONS

The results provide some support for the hypothesis that maternal use of antibiotics increases the risk of cancer in the offspring. Although recall bias is a concern, it is unlikely that this fully explains the observed effect. Further, the observed associations might be related to the underlying infections.