Breast cancer epidemiology according to recognized breast cancer risk factors in the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial Cohort

Abstract

BackgroundMultidisciplinary attempts to understand the etiology of breast cancer are expanding to increasingly include new potential markers of disease risk. Those efforts may have maximal scientific and practical influence if new findings are placed in context of the well-understood lifestyle and reproductive risk factors or existing risk prediction models for breast cancer. We therefore evaluated known risk factors for breast cancer in a cancer screening trial that does not have breast cancer as a study endpoint but is large enough to provide numerous analytic opportunities for breast cancer.MethodsWe evaluated risk factors for breast cancer (N = 2085) among 70,575 women who were randomized in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Using Poisson regression, we calculated adjusted relative risks [RRs, with 95% confidence intervals (CIs)] for lifestyle and reproductive factors during an average of 5 years of follow-up from date of randomization.ResultsAs expected, increasing age, nulliparity, positive family history of breast cancer, and use of menopausal hormone therapy were positively associated with breast cancer. Later age at menarche (16 years or older vs. < 12: RR = 0.81, 95% CI, 0.65–1.02) or menopause (55 years or older vs. < 45: RR = 1.29, 95% CI, 1.03–1.62) were less strongly associated with breast cancer than was expected. There were weak positive associations between taller height and heavier weight, and only severe obesity [body mass index (BMI; kg/m2) 35 or more vs. 18.5–24.9: RR = 1.21, 95% CI, 1.02–1.43] was statistically significantly associated with breast cancer.ConclusionThe ongoing PLCO trial offers continued opportunities for new breast cancer investigations, but these analyses suggest that the associations between breast cancer and age at menarche, age at menopause, and obesity might be changing as the underlying demographics of these factors change.Clinical Trials Registrationhttp://www.clinicaltrials.gov, NCT00002540.

Short-term effects of night shift work on breast cancer risk: a cohort study of payroll data

“…These potential confounders were based on register availability, a review of the literature, and decided upon a priori (40,41). Data were virtually complete within the time frame of available data for all variables except for female first degree relatives (5% missing).…”

Lifestyle and vitamin D dosage in women with breast cancer

“…Breast cancer has known risk factors such as the cellular aging, family history, alcohol consumption (2), overweight (3), sedentary lifestyle, and high breast tissue density (4). Other risk factors are related to women's reproductive life, which leads to increased endogenous estrogen levels, as the later age at first childbirth, early menarche, and late menopause (1,3). Some studies indicated that sun exposure and vitamin D levels are inversely proportional to the risk of developing breast cancer (5,6).…”

Awareness regarding breast self-examination among rural women - A community-based cross-sectional study

“…Breastfeeding has a protective effect. [3,5] The other important risk factors for the development of breast cancer are gender, age, and genetics. As women can do nothing about these risks, regular screening is recommended to allow early detection and thus prevent death from breast cancer.…”