Parental occupation in farming and childhood cancer risk in I4C

Ann Olsson & Joachim Schüz

- Majority of case-control studies show an association- Stronger associations with indoor pesticide exposure - Internal inconsistencies, e.g. lack of dose-response - Few cohorts show no or weaker association

Rational

Case-control studies are prone to bias!

cases controls

Years between the date of birth and the date of the interview

0

1

2

3

4

< 4 4 -< 6 >= 6

%Recall differences regarding maternaloccupational exposureto pesticides prior to conception

Information bias

[Schüz et al., Am J Epi, 2003]

[Law, Br J Cancer, 2002]

0

5

10

15

20

25

30

high

med

ium lo

w

Total Responder Non-Responder

Typical pattern:Social gradientamong controls

Selection bias

I4Cfarm

• Design: Pool prospective cohorts

• Benefits:– Data collected prior to diagnosis– Data collected closer after occurrence – Increased power to study “rare events”

0 10 20 30 40 50 60 70

Africa

Asia

South America

East Europe

West Europe

North AmericaProportion of workersemployed in agriculture

Farming around the world

Global pesticide production

• Investigate if parental occupations in different types of farming is associated with increased risk of cancer in their offspring

• Evaluate the risk of childhood cancer associated with self reported parental use of pesticides during pregnancy– Compare type and frequency reported in case-control studies

• If possible assess whether the risk of childhood cancer associated with parental exposure to occupation as a farmer and pesticides vary by exposure time-windows (preconception, prenatal, and postnatal)

I4Cfarm - objectives

I4Cfarm – study team

• IARC (Ann Olsson, Joachim Schüz, Kurt Straif)• INSERM (Jacqueline Clavel)• MCRI (Gabriella Tikellis)• NCI (Martha Linet)• CREAL (Martine Vrijheid)• Eligible cohorts (PI’s)

– MoBa, DNBC, ALSPAC, THIS, ?...

Study Country Subjects Childhood cancer

Data on occupation

MoBA Norway 108 000 106 Current job – ‘Norwegian’ ISCO-88

DNBC Denmark 100 000 100-200 Current job – Danish codes

ALSPAC UK 13 000 ~30 Lifetime jobs list, details current job - UK codes

TIHS Australia 10 628 31 Current job - 4-digit Australian ISCO codes

Eligible I4C cohorts so far…

Next steps

• Eligibility of further cohorts?

• Transfer of data to MCRI (Gabriella)

• Harmonization of disease data (Martha) and occupational data (Ann & Martine)

• Data analyses (at IARC)

• Manuscripts (Study team)