Age at initial diagnosis and prognosis of breast cancer: a nationwide multicenter retrospective study in China

Background: Several studies have indicated possible associations between age and the prognosis of breast cancer ( BC), but limited data are available from hospital-based multicenter studies in China. This study aimed to explore the associations between age at initial diagnosis of BC and the risk of recurrence or metastasis among Chinese women with newly diagnosed advanced breast cancer ( ABC) and provide treatment decision support for BC patients of different ages to medical workers. Methods: The medical records of patients newly diagnosed with ABC were obtained from 21 hospitals in seven geographic regions in China from 2012 to 2014. Patients' general information, clinicopathological features at first diagnosis, treatment information, and prognosis were retrospectively collected based on the self-designed case report form (CRF). Cox proportional hazards regression models were used to determine hazard ratios (HR) and 95% confidence intervals (CI) for the associations between age groups and the risk of recurrence and metastasis Results: A total of 1,852 cases were included in the final analysis. Age at initial diagnosis was shown to be significantly related to hormone receptor status, human epidermal growth factor receptor 2 (HER2) status, molecular subtypes, and the number of lymph node metastasis (all P<0.05). Patients aged <35 years were more likely to have bone metastasis (45.6%). Patients aged >= 65 years had a lower percentage of receiving surgery (87.1%), adjuvant chemotherapy (61.3%), adjuvant radiotherapy (35.5%), and adjuvant endocrine therapy (30.6%) than the other groups (all P<0.05). Compared with patients aged <35 years, the risk of recurrence or metastasis in those aged 55-64 years was significantly higher (HRage 55-64 =1.24, 95% CI: 1.04-1.47), and the risk of bone metastasis and lung metastasis in those aged 35-44 years was lower (HRbone metastasis = 0.74, 95% CI: 0.59- 0.93; HRlung metastasis =0.70, 95% CI: 0.53-0.93). After adjusting for stage, grade, and molecular subtype, surgery, neoadjuvant chemotherapy, adjuvant chemotherapy, adjuvant radiotherapy, adjuvant endocrine therapy, and family history of BC, patients aged 35-44 years still had a significantly reduced risk of bone metastasis and lung metastasis by 31% and 52%, respectively (HRbone metastasis =0.69, 95% CI: 0.48-0.98; HRlung metastasis =0.48, 95% CI: 0.31-0.74). Conclusions: Age at initial diagnosis is related to the clinicopathological characteristics and treatment pattern. Although the risk of site- specific metastasis varies by age, age is not an independent factor influencing the risk of total recurrence and metastasis. In accordance with current clinical practice guidelines for BC, however, precise treatment shall be chosen personally for patients whose ages at initial diagnosis are different.