Renal Cell Carcinoma (RCC)
Several types of cancer can develop in the kidneys. Renal cell carcinoma (RCC), the most common form, accounts for approximately 85% of all cases. In RCC, cancerous (malignant) cells develop in the lining of the kidney's tubules and grow into a mass called a tumor. In most cases, a single tumor develops, although more than one tumor can develop within one or both kidneys.
Early diagnosis of kidney cancer is important. 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.
Incidence and Prevalence
According to the National Cancer Institute, the highest incidence of kidney cancer occurs in the United States, Canada, Northern Europe, Australia, and New Zealand. The lowest incidence is found in Thailand, China, and the Philippines.
In the United States, kidney cancer accounts for approximately 3% of all adult cancers. According to the American Cancer Society, 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.
Smokers develop renal cell carcinoma about twice as often as nonsmokers and develop cancer of the renal pelvis about 4 times as often. Not smoking is the most effective way to prevent kidney cancer and it is estimated that the elimination of smoking would reduce the rate of renal pelvis cancer by one-half and the rate of renal cell carcinoma by one-third.
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.
The kidneys are an essential part of the body's urinary system. Each kidney is composed of about one million microscopic "filtering packets" called glomeruli. The glomeruli remove uremic waste products from the blood. Each glomerulus connects to a long tube, called the tubule. Urine made by the glomerulus moves down the tubule. Together, the glomerulus and the tubule form a unit called a nephron. Each nephron connects to progressively larger tubular branches, until it reaches a large collection area called the calyx. The calices form the funnel-shaped portion of the upper ureter (renal pelvis). Urine moves from the renal pelvis to the ureters, the large tubes that connect the kidney to the bladder.
The kidneys produce three important hormones: erythropoietin (EPO), which triggers the production of red blood cells in bones; renin, which regulates blood pressure; and vitamin D, which helps regulate the body's metabolism of calcium necessary for healthy bones.
There are several risk factors associated with kidney cancer.
There is strong evidence that cigarette, pipe, and cigar smoking doubles a person's risk for developing renal cell carcinoma (RCC). 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.
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.
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 lesions on the skin and in the central nervous system, tumor growth, and seizures.
Other Risk Factors
Additional risk factors for kidney cancer include the following:
- Age – RCC occurs most frequently in adults 50-70 years old.
- 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.
If the 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 are 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.
Computed tomography (CT scan)
CT scan is a type of x-ray that produces a series of cross-sectional, three-dimensional images of internal organs and glands. It can detect tumors and, in some cases, lymph nodes enlarged by cancer.
Magnetic resonance imaging (MRI scan)
An MRI scan uses large magnets to project magnetic waves through the body and create computer-generated, cross-sectional images of internal organs.
Ultrasound uses sound waves projected into the body to produce an image of internal organs, structures, and tumors. In this procedure, a gel is applied to the patient's pelvic and kidney areas, and a small device that emits ultrasonic pulses is slowly passed over the area. The sonic image produced is viewed on a monitor.
Intravenous pyelogram (IVP)
An intravenous pyelogram (IVP) involves injecting a dye containing iodine through a vein in the arm into the bloodstream. The dye eventually collects in the urinary system, where it improves the contrast for x-rays and produces a well-defined image of the kidneys, ureters, and bladder. By showing up as white on the dark x-ray film, the IVP can detect tumors or damage caused by a tumor in the kidney.
In some cases, the physician may request an arteriogram or venacavagram (IVP of the blood vessels that supply the kidneys) to look for tumors in the connecting arteries and veins.
A standard chest x-ray may be used to detect RCC that has has spread (metastasized) to the lungs or bones in the chest.
This nuclear imaging procedure is used to detect the spread (metastasis) of cancer to bones, when aggressive tumors and metastasis are suspected. In a bone scan, a small amount of low-level radioactive material is injected into a vein in the arm. This material discloses metastatic cancer, as well as some noncancerous diseases, in bones.
Once a diagnosis of renal cell cancer has been confirmed and the disease's stage determined, physician and patient decide on a treatment plan. 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.
It is important that the patient and physician make an informed decision together after considering all possible options, side effects, and outcomes. A confident, positive outlook can help the patient cope with the physical demands of surgery and/or therapy and can improve the chances for recovery.
A second opinion can provide additional information in the decision-making process and help the patient feel that he or she has made the right choice. Some insurance companies require a second opinion before they approve payment for treatment.
Treatment options include the following:
• Surgery (to remove cancerous tissue)
• Chemotherapy (using drugs to destroy cancer cells)
• Radiation therapy (using high-energy radiation to destroy cancer cells and shrink tumors)
• 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)
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.
Another form of treatment, called 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.
Follow-up Care and Recurrent Kidney Cancer
Patients who undergo kidney cancer surgery may experience a recurrence of the disease. For this reason, most patients undergo a regimen of follow-up examinations after surgery, typically at 3-month intervals for the first year. These examinations include a complete physical examination, chest x-ray, complete blood tests, and assessments of liver and kidney function.
If the disease recurs and remains confined to a few small areas, additional surgery may be recommended. Radiation therapy, biological therapy (immunotherapy), or chemotherapy may be used in addition to surgery (called adjuvant treatment) or to relieve symptoms (called palliative treatment).
Benign Kidney Tumors
Benign tumors are noncancerous. Most are asymptomatic, are discovered incidentally, and are not immediately life threatening.
Renal adenomas are the most common form of benign, solid kidney tumor, and are typically small, low-grade growths. Their cause is unknown. Because they usually are asymptomatic, their incidence is unknown, although one study found them present in 7% to 22% of autopsy cadavers. In rare cases, when they have grown large enough to affect kidney function or adjacent vessels, symptoms similar to those of RCC may occur.
Adenoma cells look much like low-grade RCC cells under a microscope. In fact, while they are considered benign, there is presently no known cellular classification to differentiate them from RCCs. Many researchers and physicians regard them as early stage precancers, to be treated accordingly.
Oncocytoma is a benign, usually asymptomatic tumor that can grow quite large. They can develop throughout the body and are not unique to the kidneys. Their cause is unknown, and they appear with greater frequency in men than in women. Typically, they are discovered incidentally by ultrasound, IVP, CT, or MRI scan for an unrelated health problem.
Under a microscope, many oncocytomas resemble early-stage RCCs. Many physicians regard them as precancerous growths to be surgically removed unless the patient's age or overall health condition dictates otherwise.
Also known as renal hamartoma, angiomyolipomas are rare benign tumors usually caused by an inherited genetic mutation. They can occur on an isolated, individual basis, but most often are associated with a rare genetic disease called tuberous sclerosis, which can cause tumors in the skin, kidneys, brain, and other organ systems. About 80% of persons diagnosed with tuberous sclerosis also have angiomyolipoma.
In patients without tuberous sclerosis, these tumors most often occur in middle-aged women. Most cases are discovered when the patient undergoes a CT scan for an unrelated abdominal problem, suffers gastrointestinal discomfort, or suffers a sudden hemorrhage caused by the rupture of a large tumor.
Management of the condition depends on the size of the tumors and the severity of the symptoms they produce. Asymptomatic patients and those with small tumors usually are not treated; instead, they are observed periodically with an eye toward surgery if the tumors grow or produce symptoms. Because of the potential for spontaneous rupture and life-threatening hemorrhage, patients with large tumors usually are considered candidates for some form of surgical treatment, ranging from partial nephrectomy to arterial embolization.
Fibromas are tumors of the fibrous tissue on, in, or surrounding the kidney. They are rare and are more common in women. Their cause is unknown and most do not cause symptoms. Usually they grow on the periphery of the kidney and can become large before becoming clinically obvious. While generally benign, these tumors have no special characteristics to differentiate them from malignant tumors of the kidney. Because of this uncertainty of diagnosis, partial or radical nephrectomy is the standard treatment.
Lipomas are rare renal tumors that originate in the fat cells within the renal capsule or surrounding tissue. They typically occur in middle-aged women, can grow very large, and produce pain and hematuria. Like many benign tumors, they may become cancerous and usually are treated with total nephrectomy.