Analysis of the tumor characteristics in young age breast cancer patients using collaborative stage data of the Korea Central Cancer Registry

Purpose This study aimed to evaluate tumor characteristics in young age (20-39 years old) breast cancer (YABC) patients in Korea. Materials and methods We identified 10,897 breast cancer patients from 2010 to 2015. The data were collected through 10% systematic sampling of the Korea National Cancer Incidence Database (KNCI DB). Tumor size, lymph node status, estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status were collected according to the Collaborative Stage version 2 (CSv2) Data Collection System. Results Of the 10,897 patients, 1245 (11.4%) were YABC patients. They were found to have larger tumors (T2: 41.6% in 20-39 age group vs 36.4% in 40-49 age group vs 36.5% in 50-59 age group vs 38.4% in >= 60 age group; T3: 10.1% vs 7.3% vs 6.5% vs 6.2%, P < .0001), greater rates of lymph node involvement (41.2% vs 32.7% vs 35.7% vs 32.5%, P < .0001), higher tumor grade (High grade: 26.8% vs 19.4% vs 23.5% vs 22.1%, P < .0001), and a larger proportion of triple-negative subtype (18.2% vs 11.0% vs 12.2% vs 13.5%, P < .0001). Compared to the 40-49 age group, breast cancer-related survival (BCRS) rates were worse (91.74% vs 95.04%, P < .0001), and the characteristics of YABC patients were associated with higher risk of death from breast cancer. Conclusion YABC patients have more aggressive tumor characteristics and worse survival rates. Therefore, we need to identify high-risk groups among YABC patients and support active surveillance in them. These findings from a national cohort provide important information for establishing a national cancer care strategy to manage YABC patients.