Metronomic chemotherapy in veterinary patients with cancer: rethinking the targets and strategies of chemotherapy.

Cancer chemotherapy in dogs and cats has traditionally involved administration of chemotherapy agents at the maximum tolerated dose. Cytotoxic chemotherapy has an acceptably low risk of serious toxicity, but an obligatory rest period must be included to allow for recovery of drug-sensitive normal cell populations. This rest period can also allow significant recovery of tumor cells. Metronomic chemotherapy is characterized by more frequent administration of lower doses of oral drugs and appears to halt or slow tumor progression through multiple mechanisms. This approach may be at least as effective as conventional chemotherapy with a lower risk of toxicity.