Molecular Subtypes and Prognosis in Young Mexican Women With Breast Cancer.

Introduction: Young age represents an adverse prognostic factor in breast cancer (BC), and young women present with more advanced and aggressive disease. In Latin America, BC is increasing in young women, and there is a lack of information regarding the characteristics and outcomes of this patient population.

Patients And Methods: We retrospectively analyzed a database of 4315 women treated for BC at a single institution. We compared clinical characteristics, treatment, and survival between women ≤ 40 and > 40 years of age. Survival analyses were performed for each molecular subtype.

Results: A total of 662 women (15.3%) were ≤ 40 years old. Younger women had more advanced disease, higher grade, and a larger proportion of luminal B and triple-negative tumors (P < .001). At 5 years, both disease-free and overall survival (OS) were lower in younger women, although there were no differences after adjusting for stage. Five-year OS was worse for young women with hormone receptor-positive, human epidermal growth factor receptor 2-negative subtype (82% vs. 87.1%; P = .03), but not for those with human epidermal growth factor receptor 2-positive or triple-negative disease. This difference can be attributed to luminal B tumors, which showed a worse 5-year OS in younger women (79.1% vs. 85.2%; P = .03).

Conclusion: Although young Mexican patients with BC have more aggressive disease at presentation than older women, only those with luminal B tumors have a worse survival after adjusting for stage. Strategies aimed at downstaging the disease and at improving the treatment of luminal B tumors in this population are needed.