Pau d'Arco would be a good item for kidney cancer, though I surely would not recommend it as a single item solution for kidney cancer and especially not for any cancer that had metasticized beyond its original location. Another good item for kidney cancer might be essiac tea due to as much to its cleansing properties as its moderate cancer fighting ability. For cancer that has mets I would recommend an entire diet, lifestyle and supplementation program such as the one I put together:
A great many people in Canada have followed such a protocol with success, as have a great many people in Canada successfully used the centerpiece of the protocol, oleander extract, with success. One doctor in Canada reports great success with using a combination of oleander and cesium chloride.