Abstract Background: The incidence of breast cancer among younger patients (age ≤ 40) is higher in Latin America than in other regions. The multidisciplinary approach of breast cancer cases has been related with better survival, and the knowledge about specific clinicopathological features of this population is needed to optimize the therapeutic approach. The aim of our study was to describe the clinicopathological characteristics of breast cancer in younger (Y) compared with older patients (O), and to determine which characteristics were associated with the use of primary systemic therapy. Methods: A retrospective cohort study was designed. Clinicopathological data of consecutive invasive non-metastatic breast cancer patients diagnosed between Jan 2015 to Dec 2019 in two private oncological centers in Lima, Perú were collected. Logistic regression analysis was performed to obtain models to predict primary systemic therapy as first treatment. Results: We included 503 cases (mean age 49.8 years [SD 11.8]), 30.6% younger (n = 109) and 69.4% O (n = 394). No significant differences were found for ductal histology (89% Y vs. 87.7% O, p = 0.49) and HER2-overexpression (28.4% Y vs. 23.9% O, p = 0.39). Significant differences were found for stage III (37.6% Y vs. 20% O, p < 0.01), grade 3 (44.4% Y vs 33% O, p = 0.04) and HR-positive (64.2% Y vs. 75.1% O, p = 0.03). Univariate analysis showed significant OR = 2.1 to receive primary systemic therapy for Y (95%CI 1.37 – 3.24; p < 0.01), however, multivariate analysis adjusted for age, hormone receptors (HR), HER2, grade and stage showed non-significant OR = 1.5 to receive primary systemic therapy for Y (95%CI 0.90 – 2.50; p = 0.12) as detailed in the table below: Conclusions: In our series we found a greater proportion of young breast cancer patients than previously reported. Clinical-pathological characteristics of breast cancer were different between younger and older patients, showing more aggressive phenotypes for younger patients with greater proportion of stage III, grade 3 and non-expression of hormone receptors. Decision of using primary systemic therapy in our series was based on anatomic and biologic characteristics and not on age. Citation Format: Enrique Alanya, Silvia Falcon-Lizaraso, Sebastian Aldecoa-Falcon, Franklin Aldecoa-Bedoya. Decision of Neoadjuvant Therapy in Younger vs. Older Breast Cancer Patients: A Real-World Data Analysis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-06-12.