Metronomic chemotherapy in progressive pediatric malignancies: old drugs in new package.

Despite intensive research in the field of cancer, many pediatric cancers are still incurable with current treatment protocols. Repetitive administration of conventional chemotherapy at maximal tolerated dose imposes many side effects that further limits the dosing and therefore decreases the anticancer effects. Usually limited options remain when a malignancy progresses after one or two lines of standard chemotherapy protocol. The goal of an oncologist at this point of time remains mainly palliative with an effort to halt the progression of cancer and improve quality of life. Metronomic chemotherapy is defined as the chronic administration of chemotherapeutic agents at relatively low, minimally toxic doses, and with no prolonged drug-free breaks. It is thought this type of chemotherapy inhibits tumor growth primarily through anti-angiogenic mechanisms, promoting apoptosis and immune- surveillance.