Purpose: Around 50% of patients with breast cancer in low- or middle-income countries are younger than 50 years, a poor prognostic variable. We report the outcome of patients with breast cancer 40 years and younger.

Methods: We reviewed 386 patients with breast cancer 40 years and younger and retrieved demographic, clinicopathologic, treatment-related, disease progression, and survival data from electronic medical records.

Results: The median age at diagnosis was 36 years, and infiltrating ductal carcinoma was present in 94.3% of patients, infiltrating lobular carcinoma in 1.3%, and ductal carcinoma in situ in 4.4%. Grade 1 disease was present in 8.5% of patients, grade 2 in 35.5%, and grade 3 in 53.4%; 25.1% had human epidermal growth factor receptor 2 (HER2)-positive, 74.6% had hormone receptor (HR)+, and 16.6% had triple-negative breast cancer. Early breast cancer (EBC) constituted 63.6% (stage I, 22.4%; stage II, 41.2%) of patients, whereas 23.2% had stage III, and 13.2% had metastatic disease at diagnosis. Of patients with EBC, 51% had partial mastectomy and 49.0% had total mastectomy. And 77.1% had chemotherapy with or without anti-HER2 therapy. All HR+ patients received adjuvant hormonal therapy. The disease-free survival at 5 years was 72.5% and 55.9% at 10 years. The overall survival (OS) was 89.4% at 5 years and 76% at 10 years. Patients with stages I/II had an OS of 96.0% at 5 years and 87.1% at 10 years. Patients with stage III had an OS of 88.3% at 5 years and 68.7% at 10 years. The OS of patients with stage IV was 64.5% at 5 years and 48.4% at 10 years.

Conclusion: We report survival rates of 89% at 5 years and 76% at 10 years with modern multidisciplinary management. Best results were seen in EBC: OS rates of 96% and 87% at 5 years and 10 years.