Comparison of Clinicopathological Features and Treatments between Young (≤40 Years) and Older (>40 Years) Female Breast Cancer Patients in West China: A Retrospective, Epidemiological, Multicenter, Case Only Study

The incidence of young cases of breast cancer is higher in China compared to the western world. We aimed to explore differences in risk factors, clinicopathological features and treatment modes of young female breast cancer compared to older patients in West China. We collected clinical information from 12,209 female breast cancer patients in West China, including risk factors, clinicopathological features and treatment modes, from January 2010 to December 2012. Chi-square tests and the multivariate logistic regression analysis were applied for statistical analysis. There were 2,682 young (≤40 years) cases and 9,527 older cases at the time of breast cancer diagnosis. Young patients had a greater tumor diameter at diagnosis, and a higher probability of axillary lymph node and distant metastasis (P < 0.05). The progesterone receptor positive expression rate, estrogen receptor/progesterone receptor double positive expression rate, and human epidermal growth factor receptor 2 (HER2) negative expression rate was higher in young patients compared to older patients (P < 0.05). For young patients, the age at menarche was earlier, they had lower marriage rates, fewer pregnancies and births, and a lower breastfeeding rate (P < 0.05). A higher proportion of young patients underwent advanced operations, neoadjuvant and adjuvant chemotherapy, radiotherapy, and endocrine therapy compared to older patients (P < 0.05). We found significant differences in the clinicopathological features, risk factors and treatment modes between young (≤40 years) and older (>40 years) female breast cancer patients in West China. As some of these results differ from those found in the western female population, it is likely that the mechanism of tumorigenesis of young female breast cancer patients in West China may differ from that in western developed countries. Further investigation into the regional differences in breast cancer tumorigenesis is warranted.