OBJECTIVES:  This BIA from perspective of Czech Reimbursement system aims to examine the economic impact of routine usage of the 21-Gene Assay on Adjuvant Chemotherapy in EBC patients with risk factors in Czech Comprehensive Cancer Centres (CCC) in 2016-2020. METHODS:  Eligible women with ER+, HER2-, N0, grade 2 tumours and one of the specified additional risk factors were assessed for adjuvant chemotherapy and subsequently offered Oncotype DX testing. Influence of the assay result on treatment decision were recorded. Costs of chemotherapy, medical consultation costs, administration, monitoring, and AEs management were calculated from the reimbursement database. RESULTS:  The study recruited 200 consecutive patients at 13 centres with data available for 196. The overall 63.9% of treatment recommendations changed from before to after receipt of the Recurrence Score result. The mean costs of chemotherapy are 93,700 CZK per patient. BIA evaluating the economic impact of the 21-gene assay on this patient population demonstrated that for eligible patients (at the current 23% rate of testing) the utilization of the assay results in a spending of 4,529,359 CZK in 2016 and will increase (with increasing rate of testing) to 6,906,809 CZK in 2020. CONCLUSIONS:  When used in selected population of EBC patients, the 21-gene assay reduced CT use by 62,4% with >90% of physicians indicating impact on their treatment decision. As a result of the fact, part of the reimbursement costs spent for testing is largely compensated by reduced CT usage. It is important to remember that the present analysis is a budget impact analysis and therefore focuses on short term costs. Long term costs avoided and outcomes associated with the use of the Oncotype DX test are not taken into account. Indeed, the introduction of the test into local clinical practice was consistently shown to be associated with better patients’ outcomes in over 20 studies conducted worldwide.