Epidemiological aspects on malignant diseases in childhood

University dissertation from Örebro : Örebro universitetsbibliotek

Abstract: The trends of malignant diseases in children aged 0 to 14 years, reported to the Swedish Cancer Registry 1960–1998 (n=9 298) were analyzed. The most common diagnoses were leukemia, 29.7%, tumors of the central nervous system (CNS), 27.6%, and lymphomas, 10.2%. The average annual incidence rate of childhood malignant diseases 1990–1998 was 16.19/100 000 person-years. Average annual change in incidence rate of all childhood cancer was +1.01% (95% confidence interval (CI)=0.80-1.22). Statistically significant increase was seen for leukemia +0.85% (95% CI=0.42–1.28), lymphomas +1.87% (95% CI=1.17–2.58), CNS tumors +1.45% (95% CI=1.02–1.88), sympathetic nervous system tumors +1.61% (95% CI=0.79–2.44), hepatic tumors +2.62% (95% CI=2.02–3.21), and germ cell and gonadal tumors +1.21% (95% CI=0.23–2.19).Children are exposed to persistent organic pollutants (POPs) during fetal life and breast-feeding. In a case-control study including cases of childhood cancer reported to the Cancer Registry 1988–1991 (n=962) we used breastfeeding duration as a surrogate for exposure to POPs. One matched control per case was used. Information on breast-feeding, vaccinations and chronic illness was collected from copies of the children’s Child Health Center records.Overall, breast-feeding did not affect the risk of childhood cancer, OR=1.0 (95% CI=0.7–1.3) using breast-feeding up to one month as reference. For non-Hodgkin lymphoma (NHL) OR for breast-feeding for >1 month yielded OR=5.0 (95% CI=1.1–23).No association was seen between preschool vaccinations and childhood cancer except for lymphomas and measles/measles-mumps-rubella vaccination, OR=0.2 (95% CI=0.1–0.6). Increased risk of all cancer was found for congenital malformations, OR=1.7 (95% CI=0.97–2.9), especially of leukemia, OR=3.0 (95% CI=1.5–5.8). Children with disorders of brain function had an increased risk of all cancer, OR=6.0 (95% CI=1.3–27), especially of brain tumors, OR=10 (95% CI=1.3–78).A childhood population expected to be more exposed to POPs is children of fishermen. In a register-based study, the cancer incidence rates in a cohort of fishermen children (at age 0-19 years) were compared to the rates of referent children. A modestly increased incidence rate ratio (IRR) of childhood cancer was found, IRR=1.38 (95% CI=0.96–2.00) and an increased IRR for acute lymphoid leukemia, IRR=2.65 (95% CI=1.005–6.97). In west coast fishermen children, an increased IRR was observed for NHL, IRR=3.19 (95% CI=0.98–10.4).

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