Why is metastatic cancer worse than localized cancer?
Metastatic kidney cancer is a worse disease than localized cancer because it is more difficult to completely eliminate the cancer when it has spread to multiple organs in multiple places in the body. When kidney cancer is confined to the kidney, surgery alone can be curative because the entire cancer is removed, so there are no more cancer cells remaining in the body.

In contrast, when metastatic kidney cancer is present, there are cancer cells outside of the kidney. These are difficult to treat surgically because many metastases are difficult to remove (i.e. removing every lymph node affected with cancer may not be possible) or because removing the metastatic disease may be too dangerous (i.e. when large portions of the lung or brain are affected). Also, once kidney cancer has been documented to metastasize to another part of the body, there are often microscopic deposits of the cancer that can not be detected by any tests that doctors have at their disposal. As such, removing all the identified metastatic kidney cancer may not completely eliminate the entire disease.

Patients with metastatic kidney cancer generally do less well than patients with localized disease for a number of reasons. When advanced cancer is present, patients begin to lose weight in a process known as cachexia. Symptoms of cachexia include loss of lean body mass (like muscle), increased metabolic rate, and decreased intake of food. The exact mechanism for cachexia is unknown, although a number of factors are thought to be involved in the process. Tumor cells produce chemicals known as cytokines, including tumor necrosis factor alpha (TNF-a) and interleuken-6 (IL-6). Both of these chemicals have been shown to lead to cachexia, and numerous studies have shown high levels of TNF-a and IL-6 in patients with symptoms of cachexia. In addition to the effects of cytokines, cancer and its treatment can lead to alterations in the way food tastes. As such, food may loose its appeal. The combination of decreased appetite and less appealing food leads to decreased food intake. Patients who are eating less and burning more calories through an increased metabolic rate will lose weight.

Other reasons metastatic kidney cancer is a worse disease include local effects of the cancer in the organs it metastasizes to. Lung metastases can impair lung function, making it harder to breathe, and removing the metastases involves removing significant portions of the lung, which can further decrease lung function. Metastases of kidney cancer to the liver can lead to fever, weight loss, and decreased liver function. Bone metastases of kidney cancer can lead to bone pain and fractures that do not heal well. Finally, brain metastases can be dangerous because they may directly invade important areas of the brain or lead to compression of brain tissue. Compression results from the tumor quickly growing to a large size. When these tumors are removed from the brain, important brain tissue may be removed with the tumor, which can also create problems.

Copyright 2006 Kidney Cancer Institute            

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