Anthropometric factors in relation to different tumor biological subgroups of postmenopausal breast cancer

Overweight and obesity is associated with an increased risk of postmenopausal breast cancer. However, less is known about the impact of anthropometric factors on tumor pathology and biology. A Swedish population-based prospective cohort study of 9,685 postmenopausal women not using hormonal replacement therapy (HRT) were followed for an average of 10.3 years during which 305 incident breast cancer cases were diagnosed. Invasive and sufficient tumor material was available in 248 cases. Pathological reevaluation of histological type and grade was conducted. Using a tissue microarray (TMA), the tumor expression of Ki67, HER2, ERalpha, ERbeta, PgR, cyclin D1 and p27 was evaluated. Six anthropometric factors: height, weight, body mass index (BMI), waist- and hip circumference and body fat percentage were categorized by quartiles of baseline anthropometric measurements, and relative risks were calculated using multivariate Cox regression models. Invasive breast cancer incidence was increased for women in the higher quartiles of all anthropometric measurements. Height was positively associated with Grade I and ERalpha-positive tumors. Women in the highest quartiles of weight, BMI, waist- and hip circumference and body fat percentage were all associated with tumors of ductal type, Grade II, low Ki67 index, HER2 negativity and low expression of the oncogene cyclin D1. Obesity was further associated with tumors expressing ERalpha and PgR but interestingly not ERbeta. This study confirmed previously described associations between overweight/obesity and increased risk of postmenopausal breast cancer. Furthermore, obesity was associated with tumors expressing several markers corresponding with low malignancy.