Population Attributable Fraction Estimation for Established Breast Cancer Risk Factors: Considering the Issues of High Prevalence and Unmodifiability

Abstract

Established breast cancer risk factors, in addition to being relatively unmodifiable, are highly prevalent among US women. Previous reports of population attributable fraction for the established risk factors have used definitions that resulted in 75-100% of women in the source population labeled exposed. The practical value of such estimates has not been discussed; further, the estimates have frequently been misinterpreted. In the context of examining the interpretation and public health value of such estimates, the authors demonstrate the sensitivity of the population attributable fraction to changes in exposure cutpoints. They use data from the Carolina Breast Cancer Study, a case-control study of breast cancer conducted in North Carolina between 1993 and 1996. For the four established risk factors (menarche before age 14 years, first birth at age 20 years or later/nulliparity, family history of breast cancer, and history of benign breast biopsy), the estimated population attributable fraction was 0.25 (95% confidence interval 0.06-0.48). Over 98% of the source population was exposed to at least one of these risk factors. The population attributable fraction estimate was reduced to 0.15 when more restrictive definitions of early menarche (less than age 12 years) and late age at first full-term pregnancy (30 years or more) were used (proportion exposed, 0.62). Population attributable fractions for established breast cancer risk factors probably have little public health value because of both the high proportions exposed and the relative unmodifiability of the risk factor distributions.

Alcohol Intake and Colorectal Cancer: A Pooled Analysis of 8 Cohort Studies

“…We calculated the population attributable risk, which is the proportion of cases that would be avoided if the risk factor distribution of a high-risk group switched to that of a low-risk group (36,37), by using the age-adjusted relative risk and the prevalence of alcohol intake of 30 g/d or greater (4% for women and 13% for men) from the analysis that combined studies of the same sex into a single data set. The population attributable risk was 0.9% for women and 5.0% for men.…”

Cigarette Smoking and Breast Cancer: a Case-control Study in Serbia

“…Despite the fact that breast cancer is the most common female cancer worldwide, more than half of the breast cancer risk factors remained unexplained (Madigan et al, 1995;Rockhill et al, 1998;Jemal et al, 2011). Smoking as one of the postulated risk factors for breast cancer has been a subject of numerous studies, because it is one of the few factors that could be modified (Hamajima et al, 2002;Gaudet et al, 2013;Hartz and He, 2013;Pirie et al, 2013).…”

Role of Physical Activity in Modulating Breast Cancer Risk as Defined byAPCandRASSF1APromoter Hypermethylation in Nonmalignant Breast Tissue

“…However, a large proportion of the study participants had a higher frequency of two breast cancer risk factors (25), a history of benign breast biopsies (29%) and a higher family history of breast cancer in a first-degree relative (78%; ref. 39). In addition, the study participants had a high frequency for another breast cancer risk factor, a history of exogenous estrogen use (oral contraceptives at 91% and hormone replacement therapy at 62%, if postmenopausal; refs.…”