Prognosis and adjuvant treatment effects in selected breast cancer subtypes of very young women (<35 years) with operable breast cancer.

Background: There is limited knowledge about prognosis of selected breast cancer subtypes among very young women.

Methods: We explored patterns of recurrence by age according to four immunohistochemically defined tumor subtypes: Luminal A and Luminal B (estrogen receptor positive and/or progesterone receptor positive and either human epidermal growth factor receptor 2 (HER2) positive and/or high Ki-67), HER2-positive (and) endocrine receptor absent and Triple Negative, in 2970 premenopausal patients with pT1-3, pN0-3 and M0 breast cancer.

Results: Patients <35 years of age (315, 11%) presented a significantly increased risk of recurrence and death [hazards ratio (HR) = 1.65, 95% confidence interval (CI) 1.30-2.10 and HR = 1.78, 95% CI 1.12-2.85, respectively] when compared with older patients (2655, 89%) with similar characteristics of disease. This was true considering patients with Luminal B [HR = 1.62, 95% CI 1.21-2.18 for disease-free survival (DFS) and HR = 2.09, 95% CI 0.96-4.53 for overall survival (OS)] and with Triple Negative (HR = 2.04, 95% CI 1.11-3.72 for DFS and HR = 2.20, 95% CI 1.10-4.41 for OS) breast cancer, observing the highest risk of recurrence in the younger patients with HER2-positive breast cancer (HR = 2.37, 95% CI 1.12-5.02) when compared with older patients.

Conclusions: Very young patients with Triple Negative, Luminal B or HER2-positive breast cancer have a worse prognosis when compared with older patients with similar characteristics of disease.