[Therapeutic failure of antineoplastic agents. Extracellular and cellular causes].

Chemotherapy plays an important role in the treatment of cancer. However, the drug regimens used today can only offer a cure to a small fraction of cancer patients. The article reviews the factors that limit the effect of chemotherapeutic treatment of cancer. The major cause of failure of chemotherapeutic treatment is the presence of resistant tumour cells. In addition to the various changes that may occur in tumour cells, various other factors may limit the "effective concentration" of a drug delivered to the site of the tumour, and thereby affect the overall clinical response to therapy.