Occupation and breast cancer risk in the Long Island Breast Cancer Study Project cohort

Purpose: Work is a modifiable risk factor that may influence breast cancer incidence, yet the role of specific occupations is understudied. We evaluated associations between longest held job and breast cancer incidence in the well-characterized Long Island Breast Cancer Study Project (LIBCSP). Methods: The LIBCSP, a population-based case-control study, enrolled women with first primary invasive and in situ breast cancer diagnosed between 1996-1997. Frequency matched controls were identified via random digit dialing and Health Care Finance Administration rosters. Socioeconomic (race, ethnicity, and education), reproductive (parity, age at first birth, lactation, age of menarche, family history of breast cancer, and use of oral contraceptives and hormone replacement therapy), and lifestyle (body mass index, alcohol use, and smoking status) factors were collected via interviewer-administered questionnaires. Self-reported occupational histories were coded using the 1980 Standard Occupational Classification (SOC) and 1987 Standard Industrial Classification systems, then crosswalked to the 2018 SOC and 2017 North American Industry Classification System codes. Participants without at least one occupation held for >1 year were excluded. Multivariable logistic regression estimated the odds ratio (OR) for breast cancer using longest held minor occupation group as the exposure and other longest held minor occupation groups as the reference, adjusting for key factors as above. Effect modification by menopausal status was examined. Results: Analyses included 3001 study participants (1468 cases and 1533 controls). Most participants were non-Hispanic White. Cases were older at first birth (p=0.03) and more likely to have a first degree relative with breast cancer (p <0.001). The average duration of the longest held job was 13.0 years among cases and 12.2 among controls. Most occupations were not associated with breast cancer risk. However, elevated risks were observed for financial clerks (OR=1.54, 95% confidence interval [CI] 1.10-2.14) and personal appearance workers (OR=2.02, 95%CI 1.07-3.78) compared with all other occupations when controlling for socioeconomic, reproductive, and lifestyle factors. Stratified analyses indicated increased risk among pre-menopausal financial clerks and post-menopausal personal appearance workers. Conclusions: Specific occupations, financial clerk and personal appearance worker, were independently associated with increased risk of breast cancer. Future work will seek to better understand the relationship between work and breast cancer risk by evaluating industry and occupation types based on exposure, which may further delineate why certain jobs are associated with an increased risk of breast cancer. Incorporating occupational history into population-based cancer research may identify important cancer risk prevention opportunities.