e19064 Background: Alerta Rosa is a navigation program in Nuevo Leon, Mexico that aims to reduce delays in breast cancer (BC) diagnosis and treatment initiation irrespective of healthcare coverage. Via a call center, a navigator registers each patient’s initial concern and schedules a medical evaluation. This study aimed to assess the implementation of a triage system to guide appointment prioritization for undiagnosed BC patients with abnormal breast findings or imaging studies. Methods: Women that contacted Alerta Rosa were stratified according to their clinical characteristics into three priority groups. Asymptomatic women seeking check-up information were classified as low-priority (“Green”), those with nonspecific symptoms (e.g. mastalgia) or indeterminate image studies (BIRADS 0) as intermediate-priority (“Yellow”), and patients with suspicious symptoms (i.e. palpable mass, nipple retraction or bloody discharge), abnormal image studies (BIRADS 3-5) or an established BC diagnosis as high-priority (“Red”) for an appointment. The triage system’s ability to detect undiagnosed BC was evaluated against the number of patients per category in whom BC was later confirmed. Differences in time from initial contact to first medical evaluation were explored with an independent t-test. Results: From December 2017 to 2019, 561 women with a median age of 44 years (range: 8-89) contacted Alerta Rosa. 369 (66%) reported breast symptoms, 92 (16%) sought check-up information, 68 (12%) had an indeterminate/abnormal image study and 32 (6%) had received a BC diagnosis and wanted a second opinion. Accordingly, 16% of patients were classified as “Green”, 25% “Yellow” and 59% “Red”. The median time from stratification to medical evaluation was 4 days for the “Red” group and 7 days for those in other categories ( p= 0.003). A total of 558 appointments were scheduled, of which 441 (79%) were attended. Excluding those who had received a prior BC diagnosis, 20/299 patients from the “Red” group had BC confirmed (6.7%) compared to 1/138 patient from the “Yellow” (0.7%) and none from the “Green” categories. Therefore, the “Red” category achieved a sensitivity of 95.2% (CI95%: 76.2-99.9%) and specificity of 53.8% (CI95%: 49.3-58.3%) for BC. Conclusions: The triage system adequately identified women with different probabilities of having BC. Thus, the implementation of a stratification system could help identify high risk patients in limited-resource settings where screening programs are ineffective and efforts to prioritize access to medical attention is crucial to achieve early-stage diagnoses.