The purpose of this study is to define the biologically optimal dose of vinorelbine when administered at a metronomic dosing schema. [Metronomic chemotherapy refers to the close, regular administration of minimally toxic doses of cytotoxic drugs, with minimal or no drug-free breaks, over prolonged periods]. Patients with recurrent or metastatic solid tumors are randomly assigned one of three different doses of oral vinorelbine (30 or 40 or 50 mg). Treatment is administered three times a week (Monday, Wednesday and Friday) continuously until disease progression or unacceptable toxicity or to a maximum of 24 months.