Abstract
BackgroundFew studies have investigated the association between body mass index (BMI) and breast cancer with consideration to estrogen/progesterone/human epidermal growth factor type 2 receptor status (ER/PR/HER2) in the breast tissue among Chinese pre- and post-menopausal women.MethodsFour thousand two hundred and eleven breast cancer patients were selected randomly from seven geographic regions of China from 1999 to 2008. Demographic data, risk factors, pathologic features, and biological receptor status of cases were collected from the medical charts. Chi-square test, fisher exact test, rank-correlation analysis, and multivariate logistic regression model were adopted to explore whether BMI differed according to biological receptor status in pre- and post-menopausal women.ResultsThree thousand two hundred and eighty one eligible cases with BMI data were included. No statistically significant differences in demographic characteristics were found between the cases with BMI data and those without. In the rank-correlation analysis, the rates of PR+ and HER2+ were positively correlated with increasing BMI among post-menopausal women (rs BMI, PR+ = 0.867, P = 0.001; rs BMI, HER2+ = 0.636, P = 0.048), but the ER+ rates did not vary by increasing BMI. Controlling for confounding factors, multivariate logistic regression models with BMI<24 kg/m2 as the reference group were performed and found that BMI≥24 kg/m2 was only positively correlated with PR+ status among post-menopausal breast cancer cases (adjusted OR = 1.420, 95% CI: 1.116–1.808, Wald = 8.116, P = 0.004).ConclusionsPost-menopausal women with high BMI (≥24 kg/m2) have a higher proportion of PR+ breast cancer. In addition to effects mediated via the estrogen metabolism pathway, high BMI might increase the risk of breast cancer by other routes, which should be examined further in future etiological mechanism studies.
Highlights
Breast cancer has become the most important incident cancer among Chinese women with a crude incidence rate of 41.64 per100,000
Based on a pooled data analysis from seven prospective cohort studies, high body mass index (BMI) was negatively correlated to breast cancer risk among pre-menopausal women while it was positively associated with breast cancer risk among post-menopausal women [2,5]
Numerous clinical studies found that breast cancers in post-menopausal obese women were prone to metastasizing and had poorer prognosis, which might be attributed to the differential expression of biological receptors in breast tissue [8,9]
Summary
Breast cancer has become the most important incident cancer among Chinese women with a crude incidence rate of 41.64 per100,000 (age-standardized rate of the world, 29.18/100,000). According to the China National Nutrition and Health Survey, from 1992 to 2002, the prevalence of Chinese women aged 45–59 years who were overweight and obese increased by 29.2% and 65.4% respectively [3]. The increased risk in post-menopausal obese women can likely be explained by the higher levels of estrogen released from endogenous estrone in adipose tissue. Multiple studies of Western populations have suggested that excess endogenous estrogen due to obesity contributes to an increased risk of both estrogen receptor (ER) and progesterone receptor (PR) positive breast cancer in post-menopausal women [6]. Few studies have investigated the association between body mass index (BMI) and breast cancer with consideration to estrogen/progesterone/human epidermal growth factor type 2 receptor status (ER/PR/HER2) in the breast tissue among Chinese pre- and post-menopausal women
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