The invention is based on the finding that an increased daily dose of Efavirenz should be used for the treatment of cancer compared to the daily dose used in the treatment of AIDS. The invention thus relates to the use of Efavirenz for preparing a medicament intended for the treatment of cancer, wherein Efavirenz is administered at a dose generating an Efavirenz plasma concentration in said patient superior to 3000 ng/ml. It further relates to the use of Efavirenz for preparing a medicament intended for the treatment of cancer, wherein Efavirenz is administered at a daily dose of at least 1800 mg, in particular between 1800 and 2200 mg. It also relates to the use of Efavirenz for preparing a medicament intended for the treatment of cancer, in which the daily dose of Efavirenz is optimized after administration of a preliminary daily dose and measure or Efavirenz plasma concentration. It also relates to a unique dosage form of Efavirenz, comprising Efavirenz in an amount generating an Efavirenz plasma concentration in said patient superior to 3000 ng/ml, and a pharmaceutically acceptable carrier.
