The era of chemotherapy, which started in the middle of the last century, has been ruled by the routine use of dose-intense protocols, based on the "maximum-tolerated dose" concept. By promoting a balance between patient's quality of life and the goal of rapidly killing as many tumour cells as possible, these protocols still play a prominent role in veterinary oncology.However, with the opening of a new millennium, metronomic chemotherapy (MC) started to be considered a possible alternative to traditional dose-intense chemotherapy. Characterized by a long-term daily administration of lower doses of cytotoxic drugs, this new modality stands out for its unique combination of effects, namely on neovascularization, immune response and tumour dormancy. This article reviews the rationale for treatment with MC, its mechanism of action and the main studies conducted in veterinary medicine, and discusses the key challenges yet to be solved. K E Y W O R D Schemotherapy, cytotoxic drugs, dogs, dose-intense, metronomic, review

The pain of patients who were in the terminal phase of advanced malignant tumors was successfully relieved by M-ESLON(R) capsules of controlled release morphine sulphate (10 30 60 100 mg). The most frequent side effects (sickness, vomiting, obstipation) were effectively controlled. The concentration of the drug in the plasma was stable, therefore the lasting pain relief was ensured.