Population attributable risk of invasive postmenopausal breast cancer and breast cancer subtypes for modifiable and non-modifiable risk factors

Background pulation-level impact of modifiable postmenopausal breast cancer risk factors is incompletely understood, especially regarding potential heterogeneity by estrogen receptor (ER) and progesterone receptor (PR) status. s data on 3074 cases and 6386 controls from a population-based case–control study of postmenopausal breast cancer conducted in Germany between 2002 and 2005, we calculated multivariable-adjusted odds ratios and population attributable risks (PARs) for modifiable and non-modifiable risk factors. We examined overall postmenopausal invasive breast cancer as well as tumor ER/PR subtypes. A bootstrap method provided estimates of 95% confidence intervals (95%CIs). s mmary PARs (95%CIs) for non-modifiable risk factors (age at menarche, age at menopause, parity, benign breast disease, and family history of breast cancer) were 37.2% (27.1–47.2%) regarding overall invasive tumors, 36.5% (23.3–47.6%) regarding ER+/PR+ tumors, 47.9% (26.4–64.4%) regarding ER+/PR− tumors, and 31.1% (4.0–51.9%) regarding ER−/PR− tumors. Of the modifiable risk factors (hormone therapy (HT) use, physical inactivity, BMI, alcohol consumption), HT use and physical inactivity had the highest impact with PARs of 19.4% (15.9–23.2%) and 12.8% (5.5–20.8%), respectively, regarding overall invasive tumors. For ER+/PR+ tumors, the corresponding PARs were 25.3% (20.9–29.7%) and 16.6% (7.0–26.0%). The summary PARs (95%CIs) for HT use and physical inactivity together were 29.8% (21.8–36.9%) and 37.9% (30.6–46.2%) regarding overall invasive and ER+/PR+ tumors, respectively. sions pulation-level impact of modifiable risk factors appears to be comparable to that of non-modifiable risk factors. Alterations in HT use and physical inactivity could potentially reduce postmenopausal invasive breast cancer incidence in Germany by nearly 30%, with the largest potential for reduction among ER+/PR+ tumors, the most frequently diagnosed subtype.