Mammographic density and other risk factors for breast cancer among women in China

Breast cancer is the most common neoplasm diagnosed among females in China and it is one of the leading causes of female cancer death, however the risk factors for breast cancer are not fully understood for Chinese women. One of the key risk factors shown to be relevant for westernized women is mammographic density but previously used observer Breast Imaging Reporting and Data System (BIRADS) technique to assess density is shown to have wide interand intraobserver variations. Therefore, quantitative techniques are increasingly recommended to assess this important parameter. The aim of the current study is to identify risk factors of breast cancer for Chinese women, with attention paid to mammographic density using quantitative measurements. This study was approved by the Human Research Ethics Committee of the University of Sydney (Project number: 2014/768). Women of 84 with and 987 without breast cancer were randomly selected from Fudan University Shanghai Cancer Center (FUSCC) from March 2015 to June 2016. The women with breast cancer were diagnosed within the hospital environment at FUSCC, while the other women were recruited from the Breast Cancer Screening Trail (BCST) organized by FUSCC. Demographic, lifestyle and reproductive characteristics were obtained from the registration form and the discharge summary in the health record for each woman with breast cancer and through a BCST questionnaire for breast cancerfree women. For all of the women, mammograms were acquired for cranio-caudal projection of both breasts. Mammographic density was measured by a fully automatic algorithm AutoDensity, which identifies both dense and breast areas in mammograms and then classifies mammographic density. Differences in characteristics between cancer and cancer-free women were assessed using t tests and chisquare tests. Binary logistic regression was then conducted for variables that were statistically significant from either the t test or the chi-squared test to produce odds ratios and 95% confidence intervals. Categorical variables with 0 frequency in any one of the categories were excluded from this test. The whole data set was then divided into two subsets based on menopause status, one for premenopausal and another for postmenopausal women. The statistical tests mentioned above were repeated for each subset. Table 1 shows the baseline differences of characteristics for two groups of women, and the outputs from binary logistic regression. Overall, it appears that large breast area, increasing age, increasing BMI, later age at menarche, earlier age at first delivery, longer duration of breastfeeding, postmenopause status, greater number of children, and a breastfeeding history are important agents. The results for pre and postmenopausal women are shown in Tables S1 and S2, respectively. The rest of this commentary however will focus on the implications around our findings on mammographic density. We failed to identify any association for mammographic density with breast cancer using percentage or dense area parameters, a finding which is consistent and inconsistent with previous work: one previous study which recruited 86 and 28 302 women with and without breast cancer, respectively, from a screening trial across 4 Chinese cities of similar size to our study also showed no association between density and cancer; in contrast another large cross-sectional study, involving 2527 cancer and 3394 cancer-free women, reported that, compared to women without breast cancer, mammographic density was lower and higher for cancer women within the 40-49 and 55-71 age groups, respectively, however there was no association for women aged 50-54. This difference between our work and the latter study might be explained by the fact that agedependent variations were not assessed in our work, thereby obscuring specific observations. Instead, we focused on categorizing our women based on menopausal status. Another possible Tong Li and Lichen Tang share the joint first authorship. Received: 9 January 2017 | Revised: 17 January 2017 | Accepted: 19 January 2017 DOI: 10.1111/tbj.12967