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.