(Adenocarcinoma of the Kidneys; Renal Cell Carcinoma)
Kidney cancer accounts for about 2 to 3% of cancers in adults, affecting about 50% more men than women. About 65,000 people develop kidney cancer each year and about 13,000 die of it. Smokers are about twice as likely to develop kidney cancer as nonsmokers. Other risk factors include exposure to toxic chemicals (for example, asbestos, cadmium, leather tanning and petroleum products) and obesity. People who are undergoing dialysis and develop cystic kidney disease and people with certain inherited disorders are also at higher risk of kidney cancer. People affected are usually between 50 and 70 years of age.
Most solid kidney tumors are cancerous, but purely fluid-filled tumors (cysts) generally are not. Almost all kidney cancer is renal cell carcinoma. Another kind of kidney cancer, Wilms tumor, occurs in children (see see Wilms' Tumor).
Symptoms may not occur until the cancer has spread (metastasized) or become very large. Blood in the urine is the most common first symptom, but the amount of blood may be so small that it can be detected only under a microscope. On the other hand, the urine may be visibly red. The next most common symptoms are pain in the area between the ribs and hip (the flank), fever, and weight loss. Infrequently, a kidney cancer is first detected when a doctor feels an enlargement or lump in the abdomen.
The red blood cell count may become abnormally high (polycythemia) because high levels of the hormone erythropoietin (which is produced by the diseased kidney or by the tumor itself) stimulate the bone marrow to increase the production of red blood cells. Symptoms of a high red blood cell count may be absent or may include headache, fatigue, dizziness, and vision disturbances. Conversely, kidney cancer may lead to a drop in the red blood cell count (anemia) because of slow bleeding into the urine. Anemia may cause easy fatigability or dizziness. Some people develop high levels of calcium in the blood (hypercalcemia), which may cause weakness, fatigue, slowed reaction times, and constipation. Blood pressure may increase, but high blood pressure may not cause symptoms.
Most kidney cancers are discovered by chance when an imaging test such as computed tomography (CT) or ultrasonography is done to evaluate another problem, such as high blood pressure. If doctors suspect kidney cancer based on a person's symptoms, they use CT or magnetic resonance imaging (MRI) to confirm the diagnosis. Ultrasonography or intravenous urography may also be used initially, but doctors must use CT or MRI to verify the diagnosis. If cancer is diagnosed, other imaging tests (for example, chest x-ray, bone scan, or CT of the head, chest, or both) as well as blood tests may be done to determine whether and where the cancer has spread. However, sometimes cancer that has recently spread cannot be detected. Occasionally, surgery is needed to confirm the diagnosis.
Many factors affect prognosis, but the 5-year survival rate for people with small cancers confined to the kidney is 80%. If the cancer has spread into the connective tissue around the kidney but has not spread to distant sites, the 5-year survival rate is no higher than 10%. In some instances, the goal is to focus on pain relief and other means to improve the person's comfort (see Symptoms During a Fatal Illness). As with all terminal illnesses, planning for end-of-life issues, including creating advance directives, is essential (see xref.discussed-in Legal and Ethical Concerns at the End of Life and xref.discussed-in Advance Directives).
When the cancer has not spread beyond the kidney, surgically removing the affected kidney provides a reasonable chance of cure. Alternatively, surgeons may remove only the tumor with a rim of adjacent normal tissue, which spares the remainder of the kidney. Although some nonsurgical means of destroying cancer cells are being studied, surgery is usually preferred.
If the cancer has spread into adjacent sites such as the renal vein or even the large vein that carries blood to the heart (vena cava) but has not spread to lymph nodes or distant sites, surgery may still provide a chance for cure. However, kidney cancer has a tendency to spread early, especially to the lungs, sometimes before symptoms develop. Because kidney cancer that has spread to distant sites may escape early diagnosis, metastasis sometimes becomes apparent only after doctors have surgically removed all of the kidney cancer that could be found.
If surgical cure seems unlikely, other treatments can be used, although cure rarely results. Treating the cancer by enhancing the immune system's ability to destroy it causes some cancers to shrink and may prolong survival (see Immunotherapy for Cancer). Such treatments sometimes used for kidney cancer include interleukin-2 and interferon alfa-2b. Other drugs sometimes used include sunitinib, sorafenib, axitinib, bevacizumab, pazopanib, temsirolimus, and everolimus. These drugs alter molecular pathways that affect the tumor and are thus called targeted therapies. Various combinations of other interleukins, thalidomide, and even vaccines developed from cells removed from the kidney cancer are being investigated. These treatments may be helpful for metastatic cancer, although the benefit is usually small. . Rarely (in less than 1% of people), removing the affected kidney causes tumors elsewhere in the body to shrink. However, the slim possibility that tumor shrinkage will occur is not considered sufficient reason to remove a cancerous kidney when the cancer has already spread, unless removal is part of an overall plan that includes other treatments directed toward widespread cancer.
Tumors Metastatic to the kidney
Sometimes cancers in other areas of the body spread (metastasize) to the kidneys. Examples of such cancers include melanoma; cancers of the lung, breast, stomach, female reproductive organs, intestine, and pancreas; leukemia; and lymphoma. Such spread usually does not cause symptoms. Spread is usually diagnosed when tests are done to determine how far the original cancer has spread. Treatment is usually directed at the original cancer. Occasionally, if the original cancer is treated and the tumor in the kidney is growing, the kidney tumor is removed.
Last full review/revision August 2013 by Viraj A. Master, MD, PhD