Pathological characteristics and prognosis of very young patients with early breast cancer: a comparative analysis with older patients

BACKGROUND AND PURPOSE: It has generally been established that younger breast cancer patients exhibit unfavorable biology and poorer prognosis. However, previous studies have not consistently demonstrated differences between younger and older patients. The objective of this study, therefore, was to compare pathological characteristics and prognosis in young patients (age ≤ 40 years) with early breast cancer with those of older patients (age ≥ 55 years). PATIENTS/MATERIAL AND METHODS: Individuals diagnosed with early breast cancer (age ≤ 40 years) and those ≥ 55 years of age, who were treated at two hospitals between June 2003 and December 2019, were identified. Oncological outcomes, including recurrence-free survival (RFS), distant RFS (DRFS), and locoregional RFS (LRRFS), were compared between two groups. Kaplan-Meier survival curves and the Cox proportional hazards model were used to evaluate. RESULTS: Data from 288 young (≤ 40 years) and 830 older (≥ 55 years) patients were included. Pathologically, younger patients exhibited a higher prevalence of high-grade tumors. There was no significant difference in RFS and DRFS between the younger and older patient groups (RFS: hazard ratio 1.11 [95% confidence intervals (CI) 0.74-1.66]; P = 0.613; DRFS: hazard ratio 1.03 [95% CI 0.65-1.62]; P = 0.897). However, LRRFS was unfavorable in younger patients (hazard ratio, 2.15; 95% CI, 1.03-4.49; P = 0.043). Subgroup analysis revealed a significant difference in LRRFS among hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative breast cancer patients (hazard ratio 4.04 [95% CI 1.17-13.97]; P = 0.027); however, no significant difference was observed in other subtypes. INTERPRETATION: Younger patients with breast cancer exhibited a higher frequency of high-grade tumors, although no differences were observed in RFS and DRFS. However, locoregional recurrence was more common among younger patients, especially HR-positive/HER2-negative breast cancer.