Age and Late Recurrence in Young Patients With ER-Positive, ERBB2-Negative Breast Cancer.

Importance: Young patients with breast cancer with estrogen receptor (ER)-positive, ERBB2-negative tumors have a poor prognosis. Understanding factors influencing late recurrence is crucial for improving management and outcomes. Objective: To determine whether age is an independent factor associated with late distant recurrence (DR) in young patients with ER-positive, ERBB2-negative cancers without distant metastasis within 5 years from surgery. Design, Setting, and Participants: This multicenter retrospective cohort study analyzed clinical records of patients with breast cancer who underwent surgery from January 2000 to December 2011 with at least 5 years of follow-up. The study was conducted at Samsung Medical Center, Gangnam Severance Hospital, and Seoul National University Hospital, including patients aged 45 years or younger with ER-positive, ERBB2-negative tumors, no DR within 5 years after surgery, no neoadjuvant chemotherapy, and at least 2 years of endocrine therapy. The data analysis period was from January 4, 2023, to March 21, 2024. Exposure: Age, grouped as 21 to 35 years, 36 to 40 years, and 41 to 45 years. Main Outcomes and Measures: The primary outcome was the incidence of late DR at 5 to 10 years after surgery. Survival outcomes, including late distant metastasis-free survival (DMFS), were evaluated in different age groups. Results: Among 2772 patients included, 370 (13.3%) were aged 21 to 35 years, 885 (31.9%) were aged 36 to 40 years, and 1517 (54.7%) were aged 41 to 45 years. The median (range) follow-up was 10.8 (5.0-21.4) years. The youngest group had a poorer histologic grade (eg, histologic grade 3: 107 patients aged 21-35 years [28.9%]; 149 patients aged 36-40 years [16.8%]; 273 patients aged 41-45 years [18.0%]) and more frequent chemotherapy (307 patients aged 21-35 years [83.0%]; 697 patients aged 36-40 years [78.8%]; 1111 patients aged 41-45 years [73.2%]). The youngest patients had significantly worse rates of locoregional recurrence-free survival (patients aged 21-35 years, 90.1% [95% CI, 86.8%-93.3%]; patients aged 36-40 years, 94.6% [95% CI, 93.0%-96.2%]; patients aged 41-45 years, 97.7% [95% CI, 96.9%-98.5%]), disease-free survival (patients aged 21-35 years, 79.3% [95% CI, 75.0%-83.9%]; patients aged 36-40 years, 88.7% [95% CI, 86.5%-91.0%]; patients aged 41-45 years, 94.4% [95% CI, 93.2%-95.7%]), and late DMFS (patients aged 21-35 years, 89.3% [95% CI, 86.0%-92.9%]; patients aged 36-40 years: 94.2% [95% CI, 92.5%-95.9%]; patients aged 41-45 years: 97.2% [95% CI, 96.3%-98.1%]) but not overall survival (patients aged 21-35 years, 96.9% [95% CI, 95.0%-98.9%]; patients aged 36-40 years, 98.2% [95% CI, 97.2%-99.2%]; patients aged 41-45 years, 98.9% [95% CI, 98.3%-99.5%]). Multivariable analysis showed lower hazard for late DR in the older groups compared with the youngest group (age 36-40 years: hazard ratio, 0.53; 95% CI, 0.34-0.82; P = .001; age 41-45 years: hazard ratio, 0.30; 95% CI, 0.20-0.47; P < .001). Conclusions and Relevance: In this retrospective cohort study, age was an independent factor associated with late DR in young patients with ER-positive, ERBB2-negative breast cancer. Younger age was associated with worse locoregional recurrence-free survival, disease-free survival, and late DMFS, highlighting the importance of long-term monitoring and potential for personalized treatment approaches based on age, particularly for younger patients with ER-positive, ERBB2-negative breast cancer.