Objectives Male breast cancer is a rare disease of largely unknown aetiology. In addition to genetic and hormone-related risk factors, a large number of environmental chemicals are suspected of playing a role in breast cancer. The identification of occupations or occupational exposures associated with an increased incidence of breast cancer in men may help to identify mammary carcinogens in the environment.
Methods Occupational risk factors for male breast cancer were investigated in a multi-centre case–control study conducted in eight European countries which included 104 cases and 1901 controls. Lifetime work history was obtained during in-person interviews. Occupational exposures to endocrine disrupting chemicals (alkylphenolic compounds, phthalates, polychlorinated biphenyls and dioxins) were assessed on a case-by-case basis using expert judgement.
Results Male breast cancer incidence was particularly increased in motor vehicle mechanics (OR 2.1, 95% CI 1.0 to 4.4) with a dose–effect relationship with duration of employment. It was also increased in paper makers and painters, forestry and logging workers, health and social workers, and furniture manufacture workers. The OR for exposure to alkylphenolic compounds above the median was 3.8 (95% CI 1.5 to 9.5). This association persisted after adjustment for occupational exposures to other environmental oestrogens.
Conclusion These findings suggest that some environmental chemicals are possible mammary carcinogens. Petrol, organic petroleum solvents or polycyclic aromatic hydrocarbons are suspect because of the consistent elevated risk of male breast cancer observed in motor vehicle mechanics. Endocrine disruptors such as alkylphenolic compounds may play a role in breast cancer.
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Funding The study ‘Occupational Risk Factors for Rare Cancers of Unknown Etiology’ was financially supported by the European Commission, DGXII, grants no BMH1 CT 931630 and ERB CIPD CT 940285, and the following national funding agencies. Denmark: The Strategic Environment Programme. France: Ligue Nationale contre le Cancer, Fondation de France (grant no 955368); Institut National de la Santé et de la Recherche Médicale (INSERM) (grant ‘Réseau en Santé Publique’); French Ministry for the Environment. Germany: Federal Ministry for Education, Science, Research and Technology (BMBF), grant no 01-HP-684/8. Italy: MURST, Region Piedmont; Ministry of Labour; Italian Association for Cancer Research; Compagnia SanPaolo/FIRMS. Portugal: Junta Nacional de Investidacäo Cientifica e Tecnológica, Praxis XXI, no 2/2.1/SAU/1178/95. Spain: Fondo de Investigación de la Sanitarie, Ministerio de Sanidad y Consumo, Unidad de Investigación Clinico-Epidemiológica, Hospital Dr. Peset, Generalitet Valenciana; Departmento de Sanidad y Consumo, Gobierno Vasco; Fondo de Investigación de la Sanitaria (FIS), Ministerio de Sanidad y Consumo, Ayuda a la Investigación del Departamento de Salud del Gobierno de Navarra. Sweden: Swedish Council for Work Life Research; Research Foundation of the Department of Oncology in Umeå; Swedich Society of Medicine; Lund University Hospital Research Foundation; Gunnar, Arvid and Elisabeth Nilsson Cancer Foundation; Örebro County Council Research Committee, Örebro Medical Center Research Foundation; John and Augusta Persson Foundation for Scientific Medical Research; Berta Kamprad Foundation for Cancer Research.
Competing interests None.
Ethics approval This study was conducted with the approval of the ethics committee of each European country participating in the study (Denmark, France, Germany, Italy, Latvia, Portugal, Spain and Sweden).
Provenance and peer review Not commissioned; externally peer reviewed.
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