OBJECTIVES: In France, expensive innovative drugs are paid by health insurance over and above per-case payments to hospitals. Health authorities and pharmaceutical companies set a ceiling price. Hospitals are encouraged to negotiate cheaper prices and receive bonus payments equal to half of the difference. We assessed the impact of policy decisions about Taxanes (Paclitaxel and Docetaxel) on the costs of breast cancer drugs, both for health insurance and hospitals, on the turnover of pharmaceutical companies and on the behaviours of these three stakeholders. METHODS: We conducted 1) a retrospective observational study to determine the resources allocated to chemotherapy drugs in an actual clinical setting, and 2) a prospective study simulating stakeholders’ behaviours using clinical evaluations of Taxanes, results of French epidemiological and drug use studies and published drug prices. We assessed the impact of 1) decreasing the ceiling price of Paclitaxel by 50%, and 2) excluding Paclitaxel from the list of expensive innovative drugs. RESULTS: Baseline economic data for drug use in breast cancer are: €369 million expenditure for health insurance; €0.73 million savings for hospitals, especially because of the bonus payments; and €366 million turnover of pharmaceutical companies. Decreasing the ceiling price of Paclitaxel has an impact on hospitals who then might substitute Paclitaxel to Docetaxel, but the manufacturer of Docetaxel can get the market back by lowering actual price by 3%. The impact of excluding Paclitaxel from the list of expensive innovative drugs is small for health insurance but important for hospitals who may then substitute Docetaxel to Paclitaxel. This increases health insurance expenditures and health authorities must then negotiate a lower ceiling price for Docetaxel.CONCLUSIONS: Our study shows that policy decisions modify stakeholders’ behaviours, though not always as expected. This approach could be used in the future for studying other expensive innovative drugs.