Cognitive changes associated with chemotherapy in breast cancer: an assessment of social cognition and executive functions in Peruvian patients

BACKGROUND: Cognitive impairment related to chemotherapy-commonly referred to as "chemo brain"-is a well-documented phenomenon among breast cancer patients. These impairments affect memory, attention, executive function, and social cognition, yet remain understudied in low- and middle-income countries. In Peru, where populations present a high proportion of Amerindian ancestry and distinct sociocultural factors, evidence is scarce. METHODS: We conducted a longitudinal study of 143 Peruvian women aged 28-64 years, newly diagnosed with early-stage breast cancer and naïve to chemotherapy, treated at the National Institute of Neoplastic Diseases (INEN) in Lima. Cognitive function was assessed using the Addenbrooke's Cognitive Examination (ACE), the INECO Frontal Screening Test (IFS), and a Facial Emotion Recognition (FER) task to evaluate social cognition. Baseline tests were performed before the start of treatment for each patient, and post-treatment tests were performed every 3 months. Global genetic ancestry was estimated using the ADMIXTURE algorithm based on the Affymetrix Precision Medicine Research Array. RESULTS: Native American ancestry accounted for 77.8% of the study population. Post-chemotherapy assessments revealed cognitive impairment in 21% of patients based on FER, 15% on ACE, and 12% on IFS. Higher educational attainment was associated with better cognitive performance across all domains. CONCLUSION: Chemotherapy was associated with measurable cognitive decline in a subset of Peruvian breast cancer patients. Brief and culturally adaptable tools such as the FER test offer a promising approach for routine cognitive screening in oncology settings, particularly in resource-limited contexts. Incorporating these assessments into standard care may facilitate early detection and more personalized supportive interventions.