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Open Access Research article

Space-time clusters of breast cancer using residential histories: A Danish case–control study

Rikke Baastrup Nordsborg12*, Jaymie R Meliker3, Annette Kjær Ersbøll2, Geoffrey M Jacquez45, Aslak Harbo Poulsen1 and Ole Raaschou-Nielsen1

Author Affiliations

1 Danish Cancer Society Research Center, Copenhagen, Denmark

2 National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark

3 Graduate Program in Public Health and Department of Preventive Medicine, Stony Brook University, Stony Brook, NY, USA

4 BioMedware Inc, Ann Arbor, MI, USA

5 Department of Geography, State University of New York at Buffalo, Buffalo, NY, USA

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BMC Cancer 2014, 14:255  doi:10.1186/1471-2407-14-255

Published: 11 April 2014

Abstract

Background

A large proportion of breast cancer cases are thought related to environmental factors. Identification of specific geographical areas with high risk (clusters) may give clues to potential environmental risk factors. The aim of this study was to investigate whether clusters of breast cancer existed in space and time in Denmark, using 33 years of residential histories.

Methods

We conducted a population-based case–control study of 3138 female cases from the Danish Cancer Registry, diagnosed with breast cancer in 2003 and two independent control groups of 3138 women each, randomly selected from the Civil Registration System. Residential addresses of cases and controls from 1971 to 2003 were collected from the Civil Registration System and geo-coded. Q-statistics were used to identify space-time clusters of breast cancer. All analyses were carried out with both control groups, and for 66% of the study population we also conducted analyses adjusted for individual reproductive factors and area-level socioeconomic indicators.

Results

In the crude analyses a cluster in the northern suburbs of Copenhagen was consistently found throughout the study period (1971–2003) with both control groups. When analyses were adjusted for individual reproductive factors and area-level socioeconomic indicators, the cluster area became smaller and less evident.

Conclusions

The breast cancer cluster area that persisted after adjustment might be explained by factors that were not accounted for such as alcohol consumption and use of hormone replacement therapy. However, we cannot exclude environmental pollutants as a contributing cause, but no pollutants specific to this area seem obvious.

Keywords:
Space-time cluster analysis; Breast cancer; Residential histories; Q-statistics; Denmark