An Overview of Kidney Cancer

Kidney cancer encompasses a few different diseases, though renal cell carcinoma is by far the most common type. Historically, symptoms of flank pain (pain on the side and lower back), an abdominal mass, and blood in the urine were the most common presenting signs, but today it's often suspected when a person develops anemia (a low red blood cell count), or as an "accident" when imaging tests are done for another condition. A CT scan is the most common diagnostic test, though other imaging studies may be done as well. Kidney cancer is somewhat unique in that surgery may be done even with advanced tumors. Both targeted therapies and immunotherapy drugs may be used, with chemotherapy and radiation therapy playing a lesser role than with some other cancers.

There are several types of kidney cancer, including:

  • Renal cell carcinoma: Renal cell carcinomas are by far the most common form of kidney cancer and account for nine out of 10 cases of kidney cancer.
  • Transitional cell carcinoma: Transitional cell carcinomas account for around 7 percent of kidney cancers. They arise from the same type of cells involved in bladder cancer, and transitional cell carcinoma is treated more like bladder cancer than renal cell carcinoma.
  • Wilm's tumor: Wilm's tumor is a cancer that usually develops during childhood, and among childhood cancers, is relatively common.
  • Renal sarcoma: Sarcoma of the kidney is a rare tumor that begins in the connective tissue of the kidney.

This discussion will focus primarily on renal cell carcinoma.

Kidney Anatomy and Function

Knowing a little about the anatomy and function of the kidney can help you better understand your symptoms, as well as understand how cancer in this area may affect your body.

The kidneys are composed of two bean-shaped organs, about the size of a small fist. Each kidney is located behind the abdominal organs, on each side of the spine, respectively. Some people have only one kidney, as a result of either a birth defect or illness. They can live well with only one kidney, as long as that kidney is functional.
The primary functions of the kidneys are to filter impurities, remove excess minerals and salt, and remove excess water from our blood, which are all excreted in urine. About 180 quarts (around 45 gallons) of blood is filtered through our kidneys every day, to produce approximately 1 to 2 quarts of urine. The urine then travels down tubes, called ureters, and is stored in the bladder until excretion (urination).

Within the kidney are more than a million nephrons, the functional unit of the kidney. Each nephron is made up of a glomerulus and a tubule. Kidney cancer (renal cell carcinoma) is thought to arise from the tubules of the nephrons.

Symptoms 

Unfortunately, kidney cancer symptoms do not usually appear until the disease has progressed. In fact, the most common presenting sign of kidney cancer is a low red blood cell count (anemia). When symptoms occur, some of these may include:

What Are the Signs and Symptoms of Kidney Cancer?

Causes and Risk Factors

While we aren't certain of the exact causes, researchers have identified several risk factors for kidney cancer. Some of these include:

  • Age: The risk of kidney cancer increases with age, with most renal cell carcinomas occurring over the age of 40. (In contrast, Wilm's tumor is more common in children.)
  • Sex: Kidney cancer is more common in men than in women.
  • Race: Kidney cancer is slightly more common in blacks and American Indians.
  • Smoking: People who smoke have an increased risk of kidney cancer.
  • Occupation: Workplace exposures to chemicals and substances such as asbestos, benzene, and more
  • Obesity
  • A family history of kidney cancer or certain genetic syndromes
  • Some medications
What Are the Causes of Kidney Cancer and Who Is at Risk?

Diagnosis

The diagnosis of kidney cancer may be suspected based on anemia, blood in the urine, physical symptoms, and other lab test abnormalities, and is often made with a combination of imaging tests. Many times, the finding of a mass on a radiographic study, such as an X-ray, CT scan, or MRI, during an investigation for another condition may lead a physician to suspect kidney cancer. 

The initial test when kidney cancer is suspected is often an ultrasound. An ultrasound uses sound waves to create a picture and can distinguish solid tumors from cysts. CT (computerized tomography) is perhaps the most helpful test and can be used for both detection and staging of kidney cancer. CT uses a series of X-rays to create a 3-dimensional picture of the inside of the body. An MRI (magnetic resonance imaging) may be done for people who are unable to have a CT (due to allergies to CT contrast materials or poor kidney function). MRI uses magnetic imaging rather than x-rays. MRI is also helpful if a tumor is thought to have spread into veins near the kidneys. Sometimes a PET scan or bone scan is done to help with staging a kidney tumor.

Unlike many tumors, a biopsy is not often needed to diagnose kidney cancer. A biopsy, when needed, may be done in a few different ways, and allows pathologists to look for the presence of cancer cells under the microscope. Samples of a kidney cancer are very helpful in guiding treatment with targeted therapies but are often obtained during surgery to treat the cancer, rather than during the diagnostic process.

Staging

If cancer is found, more tests may need to be done to determine if the kidney cancer has spread to nearby tissues or other organs. This is called staging.

Kidney cancer is staged by measuring the size of the tumor within the kidney's structures, including the cortex and renal pyramid, as well as any evidence of spread to nearby tissues or distant regions of the body. Stage 1 tumors are confined to the kidney's cortex—it's outer perimeter. Stage 2 tumors are larger in size but are still confined within the kidney. Stage 3 tumors spread to nearby blood vessels, and stage 4 tumors spread outside the kidney's outer lining and can also spread to nearby organs.

What Tests Are Done to Find Kidney Cancer?

Treatment

Treatments for kidney cancer depend upon the stage of the disease, as well as many other factors, such as your general health, the location of the cancer in the kidney, and more. 

Most people with kidney cancer will have some type of surgery. Those who have early-stage kidney cancer are the best candidates for surgery, but kidney cancer is one of the few solid tumors in which surgery may be beneficial even with advanced metastatic disease (stage 4). While surgery is the treatment of choice for most kidney cancers, this can be difficult in very elderly people or those with multiple serious medical conditions. For those who would not tolerate surgery, treatments such as cryosurgery (freezing the tumor), or radiofrequency ablation (burning the tumor), may be options.

Several targeted therapy drugs have been approved for use in some people with advanced kidney cancer. These drugs block and prevent the growth and spread of malignant cells. They do this by directly interfering with a pathway involved in the growth of cancer, or by preventing the growth of blood vessels needed to supply the tumor with nutrients (they inhibit angiogenesis). The side effects of these drugs are different from those of chemotherapy and frequently are better tolerated.

Immunotherapy, also known as biologic therapy, is a newer treatment approach for cancer, that works simplistically by stimulating the body's own immune system to fight off cancer cells. There are a few different categories of these drugs that have been found to be effective for kidney cancer.

In addition to the approved treatment options available, there are currently many clinical trials in progress, looking for newer or better therapies to treat kidney cancer. Unlike the myths of clinical trials so many have heard, some of these trials now offer people the opportunity to use treatments that are likely to improve their outcomes. It may be helpful to keep in mind that every treatment we currently have for cancer was once studied in a clinical trial, and at the current time, both treatments for, and survival rates from, kidney cancer are improving.

Radiation is not commonly used as a treatment for kidney cancer but may be used "palliatively," to relieve discomfort caused by the effects of the cancer spreading. Chemotherapy has only a limited effect against renal cell carcinoma.

Palliative care, care that focuses on treating the symptoms of cancer and improving quality of life, is very important, even for people who have early-stage tumors that are likely to be cured.

What Treatments Are Used for Kidney Cancer?

A Word From Verywell

In order to find kidney cancer in the earliest possible stages, it's important for people to be aware of the potential symptoms of the disease, as well as their risk factors. When diagnosed, there are now many options for treatment.

That said, an ounce of prevention beats a pound of cure, and there are many simple things people can do to reduce their risk. Quit smoking or don't start, as this is a strong risk factor. Risk does decrease when you quit, so it's never too late, and there are many reasons to quit smoking after a diagnosis of cancer even if you've been diagnosed with the disease. Take the time to learn about any chemicals or other substances you are exposed to at work, and follow the recommended precautions. Finally, eating a healthy diet to maintain a healthy weight is important, as obesity is a risk factor for many cancers, not just kidney cancer.

What Are the Signs and Symptoms of Kidney Cancer?
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