Which patients may benefit from the use of a decision support system to improve compliance of physician decisions with clinical practice guidelines: a case study with breast cancer involving data mining.

OncoDoc2 is a guideline-based clinical decision support system (CDSS) for breast cancer management. It has been used as an intervention in a randomized controlled trial carried out to evaluate the impact of using a CDSS upon the compliance with clinical practice guidelines (CPGs) of multidisciplinary staff meeting decisions. Data mining was used to discover multi-criteria regularities as "emerging patterns" (EPs) associated with compliance and non-compliance with CPGs when using and not using OncoDoc2 and to assess which patients may benefit from the use of the CDSS. Decision data was collected from all participating centers. The number of EPs associated with non-compliance is smaller in the intervention arm, which suggests a practice harmonization effect of OncoDoc2. EPs associated with compliant decisions in both arms of the trial correspond to situations well identified in CPGs. EPs associated with non-compliant decisions when the system is not used are associated with compliance when the system is used except in clinical situations where evidence is lacking