Sarah,
High dose Interleukin-2 has been shown to have the best record for lasting remissions for those who respond to it; Sutent has less severe side effects but is too new to tell if the remissions will last. High dose Interleukin-2 has tough side effects and is usually administered in the hospital; some hospitals routinely admit IL-2 patients to the ICU ofr treatment. Because the side effects are severe, physicians do not use it for cancers that are more responsive to conventional chemotherapy or radiation than RCC; it is most often used to treat renal cell and melanoma patients.
It sounds as if you have good doctors. A person with metastatic disease should have the cancerous kidney removed, and should be treated by an oncologist who has experience in treating renal cell carcinoma patients. especially if they have a subtype less common than the most common clear cell. The Kidney Cancer Association has a list of experienced doctors (call them at 800-850-9132) but many very good doctors are not on their list. There is an email support group specific to kidney cancer; join it at
http://cancerguide.org/kofaq/ .