Background: The role of occupational exposures in breast cancer development is still uncertain. A recent paper showed increased risks in some occupational sectors in Lombardy, Italy. We deepened this analysis at the level of single provinces of the same Italian region.
Methods: Based on administrative data, a case-control study was carried out recruiting all incident cases of female breast cancer in the period 2002-2009, aged between 35 and 69 years, residing in Lombardy, Italy. Controls were randomly sampled from all women residing in Lombardy as of December 31, 2005. Occupational histories, including blue collar status, were available from 1974 through record linkage with a social security pension database, and were obtained for 11188 cases and 25329 controls. Adjusted odds ratios (ORs) and corresponding 90% confidence intervals (CIs) were calculated using multiple unconditional logistic regression models. Analyses were performed also by single provinces of Lombardy, Italy. Multiple comparisons were accounted for according to the Benjamini-Hochberg method.
Results: The ORs for female breast cancer were modestly but significantly increased for employment in electrical manufacturing (OR 1.12, 90% CI 1.04-121), textile (OR 1.08, 90% CI 1.02-1.15), paper (OR 1.25, 90% CI 1.06-1.46) and rubber (OR 1.26, 90% CI 1.03-1.54) industries. Analysis by province showed significantly increased ORs for electrical manufacturing in the Milano province. After adjustment for multiple comparisons no estimates remained statistically significant, except OR for electrical manufacturing in the Milano province.
Conclusions: Although with several limitations, our results point to a possible role of exposures in electrical manufacturing, textile, paper and rubber industries in the process leading to breast cancer. An in-dept study for the electrical manufacturing industry has been already planned in Milano province.