Kidney Cancer

Several types of cancer can develop in the kidneys.  Renal cell carcinoma, the most common form, accounts for approximately 85% of all cases. Renal Cell Carcinoma (RCC) involves cancerous cells developing in the lining of a kidney's tubules and growing into a mass (tumor).  In most cases, a single tumor develops, although more than one tumor can develop within one or both kidneys.

Incidence; Contributing Risk Factors

In the United States, kidney cancer accounts for approximately 3% of all adult cancers.  According to the American Cancer Society at the time of writing, about 32,000 new cases are diagnosed and about 12,000 people die from the disease annually.  Kidney cancer occurs most often in people between the ages of 50 and 70, and affects men almost twice as often as women.

Wilms' tumor accounts for about 6% of childhood cancers and is the most common type of kidney cancer in children.  Incidence of Wilms' tumor is higher in girls younger than the age of 5 and in African Americans.

There are several risk factors associated with RCC:

• Smoking. There is strong evidence that cigarette, pipe, and cigar smoking doubles a person's risk for developing RCC and puts them at 4 times the risk of developing cancer of the renal pelvis.  Researchers estimate that 25% to 30% of all renal cell cancers are directly attributable to smoking.
• Overuse of Painkillers. Medications containing phenacetin, which were once commonly used over-the-counter painkillers, have been linked to RCC, typically in patients who used them to excess.  While these drugs were removed from U.S.  markets more than 20 years ago, older Americans who used them may be at risk for RCC.
• Chemical Exposure. Studies have shown that exposure to certain substances increases the risk of RCC.  Asbestos, once commonly used as an insulating material, and cadmium, formerly an ingredient in certain colored inks and paints, have been linked to kidney cancer.  People who may have come into contact with these substances, such as construction and shipyard workers, painters and printers, may have an increased risk for RCC.
• Genetics. People with a family history of kidney cancer are at increased risk for RCC.  It is suspected that inherited genetic mutations may be the cause, perhaps triggered by damage to the DNA that forms genes; cigarette smoke, for example, is known to contain chemicals that can damage the genes of kidney cells.
  
  Other genetic mutations may cause two rare forms of kidney cancer.  Von Hippel-Lindau syndrome is a disease that causes multiple tumors of the brain, spine, eyes, adrenal glands, pancreas, inner ear, testicles, and kidneys.  Tuberous sclerosis is a disease characterized by small tumors of the blood vessels, which result in numerous bumps on the skin, mental retardation, seizures, cysts in the kidneys, liver, and pancreas and RCC.
• Age. RCC occurs most frequently in adults aged 50 - 70 years.
• Diet and weight. High-fat diet and obesity may increase the risk for RCC.
• Extended dialysis. Patients treated with long-term dialysis may develop cysts in their kidneys, a risk factor for RCC.
• Estrogen. Test animals have developed RCC when given estrogens.
• Gender. Men are twice as likely as women to develop RCC.

Signs and Symptoms

The primary symptoms of RCC include the following:

• An abdominal mass or lump
• Blood in the urine (hematuria)
• Fever
• High blood pressure (hypertension)
• Pain in the side (flank) or lower back not associated with injury
• Persistent fatigue
• Rapid, unexplained weight loss
• Swelling (edema) in the legs and ankles.

Diagnosis and Tests

Early diagnosis of kidney cancer is important.  If a physician suspects RCC, a series of examinations, procedures and laboratory tests are performed to confirm the diagnosis.  A thorough physical examination is performed to assess the patient's health and obtain information about symptoms and a medical history is taken to determine if there are risk factors for RCC.  One or more imaging tests may be performed to obtain pictures of the kidney(s) and locate abnormalities.  Some imaging tests require the injection of a special "tracer" material (dye or low-level radioactive isotope) into the patient's bloodstream.  These tests include:

• Computed tomography
• Magnetic resonance imaging
• Ultrasound
• Intravenous pyelogram
• Chest X-ray
• Bone scan

Laboratory tests may also be performed, including:

• Urinalysis
• Blood tests to detect
  
  • Anemia (too few red blood cells; caused by internal bleeding, a common cancer symptom)
  • Polycythemia (too many red blood cells; sometimes caused by cancerous tumors in the kidney that trigger the release of erythropoitin [EPO], a hormone that increases red blood cell production in bone marrow)
  • Hypercalcemia (high blood calcium levels) and elevated liver enzymes.
• Cystoscopy (to rule out blood in the urine that results from other health problems such as kidney stones or traumatic kidney injury)
• Fine needle aspiration.

Treatment and Prevention

Factors that are considered include the patient's age and overall health and the extent to which the cancer has spread.  For example, a patient with one healthy, functioning kidney and one afflicted with an aggressive Stage 2 RCC is a more likely candidate for radical surgery than a patient with only one kidney and a less aggressive Stage 1 cancer.

Aside from surgery, chemotherapy or radiation therapy, treatment options include the following:

• Hormone therapy (using hormones to prevent cancer cell growth)
• Biological or Immunotherapy (using compounds produced by the body's immune system, or laboratory-produced copies of them, to destroy cancer cells).
• Arterial Embolization is reserved for patients whose health does not permit surgery, such as those with heart or lung disease.  In arterial embolization, a very small tube (catheter) is inserted through a blood vessel in the groin and passed up to the kidney.  A small piece of gelatin sponge is then injected into the artery that supplies blood to the cancerous kidney.  This cuts off the flow of blood to the kidney and the cancerous tumor, and both die.  The kidney usually is surgically removed at a later date, if and when the patient's health permits.
• Gene Therapy is being explored by researchers who think inherited genetic mutations may cause many cases of RCC.  Eventually, a process that uses normal genes to overcome or reverse the cancer-causing process may be developed.

Two or more forms of treatment may be used in combination, such as surgery to remove a primary tumor followed by radiation treatment or chemotherapy to kill cancer cells that may remain in the body.

Prognosis

As with most types of cancer, the earlier the tumor is discovered, the better a patient's chances for survival.  Tumors discovered at an early stage often respond well to treatment.  Survival rates in such cases are high.  Tumors that have grown large or spread (metastasized) through the bloodstream or lymphatic system to other parts of the body are more difficult to treat and present an increased risk for mortality.

Renal cell cancer is unpredictable.  It is the second most common tumor to undergo spontaneous regression following removal of the primary lesion; this occurs about 0.5% of the time.  Another unusual characteristic of RCC is the variability in the growth of the primary tumor.

Once metastasis occurs, prognosis depends on the extent of the spread and the interval between appearance of metastases and the removal of the kidney.

Overall, the 5-year survival rate for RCC (all stages combined) is about 40-45%.