Objective. To estimate the cost of common versus normative practice in the treatment of breast cancer (BrCa) at the Mexican Institute of Social Security and Services for GovernmentWorkers (ISSSTE). Materials and methods. A process approach from the perspective of providers. We identified the resources utilized during one year of treatment through online questionnaires administered to oncologists in various hospitals (common treatment) as well as by conducting a clinical guidelines review (normative treatment). Results. The cost of common treatment was USD113.6 million annually. For stage I cases, it proved 1.23 and 1.12 times higher in regional and general as opposed to highly specialized hospitals. For stages 0-II cases, it was higher than normative treatment owing to greater use of consultations and chemotherapy. Conclusions. BrCa accounts for 3.8% of the ISSSTE budget in 20l7.Achieving greater efficiency in the use of resources allocated for BrCa treatment requires stricter adherence to clinical guidelines as well as early detection.