This document discusses the implementation of decision support methods and tools to improve the management of breast cancer patients. It describes how multidisciplinary tumor boards discuss treatment plans for patients but that guidelines do not cover all cases. The DESIREE project aims to provide recommendations using multiple reasoning approaches: guideline-based using formalized guidelines, data-based using predictive algorithms on large patient databases, and case-based using similarity measures between patient cases. One tool discussed is OncoDoc, a guideline-based clinical decision support system shown to increase compliance with guidelines in multiple studies over 18 years.