The Impact of Young Age on Breast Cancer Prognosis: A Systematic Review and Meta-Analysis

INTRODUCTION: There is no consensus on the impact of young age (≤ 35 or 40) on breast cancer prognosis. In this study, a meta-analysis was carried out on the prognosis of breast cancer in young women. METHODS: We searched PubMed, Embase, Web of Science, Cochrane, and key cancer-related international conference proceedings, from their inception to 1st June, 2023, with an update on 15th July, 2023. Studies were included if they reported hazard ratios (HRs) with 95% confi-dence intervals (CIs) or presented Kaplan-Meier survival curves. The main outcomes were overall survival (OS), disease-free survival (DFS), breast cancer-specific survival (BCSS), lo-cal recurrence-free survival (LRFS), distant disease-free survival (DDFS), progression-free survival (PFS), and pathological complete response (pCR). This meta-analysis was registered in PROSPERO (CRD42023459282). RESULTS: The meta-analysis, including 129 studies with approximately 1,065,000 patients, re-ported that young breast cancer (YBC) patients had worse OS (HR = 1.30; 95% CI: 1.17 - 1.43; I² = 93%; P < 0.01), DFS (HR = 1.58; 95% CI: 1.47 - 1.70; I² = 68%; P < 0.01), BCSS (HR = 1.28; 95% CI: 1·09 - 1.49; I² = 95%; P < 0.01), LRFS (HR = 2.05; 95% CI: 1.59 - 2.59; I² = 70%; P < 0.01), DDFS (HR = 1.44; 95% CI: 1.11 - 1.87; I² = 91%; P < 0.01), and PFS (HR = 1.54; 95% CI: 1.16 - 2·03; I² = 90%; P < 0.01) and a greater pCR rates than non-young breast cancer (NYBC) patients (odds ratio (OR) = 1.45; 95% CI: 1.16 - 1.82; I² = 87%; P < 0.01). Subgroup analysis demonstrated that, compared with NYBC patients, certain differences were found in the prognoses of YBC patients with different molecular subtypes, regions, and stages. DISCUSSION: This meta-analysis confirmed that YBC patients have worse survival outcomes than NYBC patients, despite having higher pCR rates. Subgroup analyses demonstrated that outcomes varied by molecular subtype, region, and disease stage. These findings underscore the importance of early screening, enhanced patient education, and tailored treatment strategies for YBC patients. CONCLUSION: Patients with YBC had worse OS, DFS, BCSS, LRFS, DDFS, PFS, and greater pCR rates than NYBC patients.