Background and research question: Loss of exclusivity of oncology drugs causes an important drop in their price due to the marketing of generic medicines. In this article we study how the price of certain oncology drugs evolves throughout time after the loss of their patent, both in terms of the notified price and at a level of the public tenders for the purchase of medicines. Methods: The variation in the price of oral oncology drugs was assessed from the public information provided by the Interministerial Medicinal Products Pricing Committee (Comisión Interministerial de Precios de los Medicamentos, CIPM) and the data from public tenders for the purchase of medicines. Results: The data show a significant drop in price of the medicines assessed after the expiry of their patent, both at a notified price level (70% of average drop in price in 2.6 years) and at the level of the public tenders (drops exceeding 90% in a year for the most innovative drugs). Discussion: The drop in the price of the oncology drugs after the expiry of their patent is seen in all the medicines assessed. The trends seen allow to predict the evolution of the price of another innovative medicine that is nearing the expiry of its patent (Lenalidomide), with an expected drop in price by 90% with respect to the current price of the innovative drug.