OCCUPATIONAL RISK FACTORS FOR BREAST CANCER: FINDINGS FROM THE NEW ZEALAND BREAST CANCER STUDY

Amanda ENG, Massey University, New Zealand
MANNETJE A. 1 , MCKENZIE F. 2 , JEFFREYS M. 3 , FIRESTONE R. 1 , PEARCE N. 4 , ELLISON-LOSCHMANN L. 1

1 Centre for Public Health Research, Massey University, Wellington, New Zealand
2 Section of Environment and Radiation, International Agency for Research on Cancer, Lyon, France
3 School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom
4 London School of Hygiene and Tropical Medicine, London, United Kingdom

Purpose
To investigate the association between occupational risk factors and breast cancer risk in Māori and non- Māori women in New Zealand (NZ).
Methods
A population-based case-control study was conducted to examine risk factors for breast cancer among three different ethnic groups in NZ: Māori, Pacific, and non- Māori /non-Pacific (NM/NP). All women registered on the NZ Cancer Registry with primary invasive breast cancer between 2005-2007 were eligible for inclusion. Controls were identified from the NZ Electoral Roll and matched on ethnicity and frequency matched on 5-year age bands. All participants completed comprehensive questionnaires on health and lifestyle behaviours including socio-demographics, lifestyle, and work and reproductive histories. Participants were asked to list all of the jobs that they ever held including whether they worked night shift. Unconditional logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (CI) adjusted for established breast cancer risk factors and socioeconomic status.
Results
The analysis focused on Māori and NM/NP women due to the small number of Pacific women in the study and included 1729 cases (1418 NM/NP and 311 Māori) and 2350 controls (1482 NM/NP and 868 Māori).  NM/NP women who ever worked as an industrial plant operator showed an elevated OR of 1.60 (95% CI 0.81-3.18; there were too few Māori women in this category for analysis). Māori women who ever worked as a labourer/packer showed a modestly elevated OR of 1.43 (95% CI 1.07-1.91). There was no clear evidence of an increased risk for ever having worked a night shift for either ethnic group.
Conclusion
These preliminary findings suggest an elevated breast cancer risk for certain occupational groups and ethnic differences in breast cancer risk for the lowest skill-based occupational category.  
Funding source
The study was partially supported by the Cancer Society and Massey University Research Fund.