Doctor: Paula Rios Fernandez
Title: Perinatal and environmental risk factors of childhood neuroblastoma
Supervisor: Jacqueline Clavel
Doctoral school: ED 393 Epidemiology and Biomedical Information Sciences, Université Paris Cité
Date of thesis defense: 05/2019
Jury: Jacqueline Clavel, Babak Khoshnood, Béatrice Fervers, Cécile Chevrier, Gudrun Schleiermacher, Nadia Haddy
Neuroblastoma is the most common extra-cranial tumor in children. Little is known about the etiology of neuroblastoma. The early age at onset and the embryonic nature suggest a role for perinatal exposures. In this work, we analyzed whether childhood neuroblastoma was associated with specific perinatal characteristics and environmental exposures around pregnancy. We assessed the following birth-related characteristics: gestational age, birth-weight and fetal growth, and the presence of congenital malformations. The maternal reproductive history before the index pregnancy and maternal intake of folic acid or vitamins/minerals before or during pregnancy was also assessed. With regards to environmental exposures related to parental habits, we focused on maternal use of household pesticides during pregnancy, parental smoking and maternal alcohol consumption. Methods: We conducted a pooled analysis of two French national-based case-control studies. The mothers of 357 neuroblastoma case and 1,783 control children younger than 6 years, frequency-matched by age and gender, completed a telephone interview that focused on sociodemographic and perinatal characteristics, childhood environment and parental lifestyle. Unconditional logistic regression was used to estimate pooled odds ratios (OR) and 95% confidence intervals (CIs), including matching variables, study of origin and potential confounders. A meta-analysis of our findings with those of previous studies was also conducted with regards to maternal smoking and alcohol consumption during pregnancy. We used random effects, precision-based weighting to calculate the summary OR including our results. Results: The first part of the thesis focused on perinatal characteristics. We observed that being born either small (OR 1.4 [95% CI 1.0-2.0]) or large (OR 1.5 [95% CI 1.1–2.2]) for gestational age and, among children younger than 18 months, having congenital malformations (OR 3.6 [95% CI 1.3–8.9]), were significantly associated with neuroblastoma. Inverse associations were observed with breastfeeding (OR 0.7 [95% CI 0.5–1.0]) and maternal use of any supplements containing folic acid, vitamins or minerals (OR 0.5 [95% CI 0.3–0.9]) during the preconception period. The second part of the thesis showed that maternal use of any type of household pesticide during pregnancy was associated with neuroblastoma (OR 1.5 [95% CI 1.2–1.9]). The most commonly used type of pesticides were insecticides and there was a positive association with their use alone (OR 1.4 [95% CI 1.1–1.9]) or with other pesticides (OR 2.0 [95% CI 1.1–3.4]). In the third part, our analyses showed that maternal smoking during pregnancy was slightly more often reported for the cases (24.1%) than for the controls (19.7%) (OR 1.3 [95% CI 0.9–1.7]; Paternal smoking in the year before child’s birth was not associated with neuroblastoma as independent exposure (OR 1.1 [95%CI 0.9–1.4] but the association was stronger when both parents reported having smoked during pregnancy (OR 1.5 [95% CI 1.1–2.1]. Finally, in a meta-analysis of maternal smoking and neuroblastoma the summary OR from meta-analysis was 1.1 [95% CI 1.0–1.3]. Conclusions: Our findings support the hypothesis of a defective embryogenesis in neuroblastoma since fetal growth anomalies and congenital malformations were associated with an increased risk of neuroblastoma. This work also adds to the evidence of an association between neuroblastoma and some exposures during pregnancy, such as maternal use of household pesticides and maternal smoking, which are additional reasons why to advise pregnant women to limit these exposures in this period. Further investigations are needed to clarify the role of folic acid supplementation and breastfeeding, given their potential importance in neuroblastoma prevention.