Kidney cancer makes up 4-5% of the cancers diagnosed in the United States[1], and is more common in men than women. The average age at diagnosis is 65. Kidney cancer is uncommon before the age of 45.
The kidneys’ main role in the body is removing excess water, salt, and waste from the blood, and turning these into urine for the body to excrete via the bladder. The kidneys also produce hormones that regulate blood pressure and red blood cell levels in the body.
Early kidney cancers often don’t cause any symptoms, but as the disease progresses, it may cause:
Blood in the urine
Low back pain on one side (not explained by injury)
A lump on the lower back or side of the trunk
Weight loss and loss of appetite
Anemia
Fatigue
Lingering fever not caused by infection
These symptoms may be caused by any number of health conditions, and should be evaluated by a medical professional.
Kidney cancer can present with various subtypes, each characterized by distinct features and biological behaviors:
Renal cell carcinoma (RCC): This is by far the most common form of kidney cancer, accounting for about 90% of diagnosed kidney cancers. Usually RCC forms as a single tumor in the kidney, though it is possible for multiple tumors to form in one kidney, or for tumors to arise in both kidneys. There are several subtypes of RCC; determining the subtype with your doctor will help decide the course of treatment.
Urothelial carcinoma: These cancers begin in the lining of the renal pelvis, where the ureters meet the kidneys. This region is lined with transitional cells, the same cells that line the bladder and ureters. Urothelial carcinomas in the kidney look very similar to those in the bladder and are similarly tied to smoking and exposure to certain workplace chemicals.
Renal sarcoma: This rare form of kidney cancer begins in the blood vessels or connective tissue of the kidneys. These account for less than 1% of all kidney cancers.
Wilms tumor: This form of kidney cancer almost always occurs in children, and is exceedingly rare in adults.
In addition to these forms of kidney cancer, some individuals may experience benign kidney tumors, which may require treatment.
Kidney cancer are on how far the cancer has spread:
Localized: There is no sign the cancer has spread beyond the kidney.
Regional: The cancer has spread to nearby structures or lymph nodes
Distant: The cancer has spread to distant parts of the body, such as the liver or bones.
Incidence
Below is the overall incidence of kidney cancer by gender and age group:
As previously noted, men are about twice as likely to develop kidney cancer as women.
Risk Factors
There are several confirmed risk factors that contribute to an individual’s risk for kidney cancer:
Biological sex: Men are about twice as likely to develop kidney cancer as women; for people assigned male at birth, the overall lifetime risk of developing kidney cancer is about 1 in 43, whereas for people assigned female at birth, that risk decreases significantly to 1 in 73.
Smoking & secondhand smoke exposure: Smoking and secondhand smoke increases your risk of kidney cancer significantly, and the risk seems to correlate with how much you smoke. Tobacco smoke contains numerous carcinogens that can lead to genetic mutations and uncontrolled cell growth, ultimately resulting in cancer. Quitting smoking at any age can significantly reduce the risk of cancer and other smoking-related diseases. The body begins to repair itself almost immediately after quitting, with the risk of cancer decreasing over time. Even individuals who have smoked for many years can benefit from quitting, as the risk decreases with each year of abstinence.
Meat consumption: Both red meat and non-red meat consumption has been associated with an increased risk for kidney cancer. The risk may be amplified depending on how the meat is cooked. When meat is cooked at high temperatures or over an open flame (such as through grilling), carcinogenic compounds known as heterocylic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) are formed.[2]
Workplace chemical exposure: Workplace exposure to the chemicals trichlorethylene[3] (commonly used as a metal degreaser and in dry cleaning) and cadmium (most common in the manufacturing, construction, and waste management sectors) has been shown to increase the risk of kidney cancer.
Health conditions:
High blood pressure: High blood pressure increases the risk of kidney cancer, and the use of blood pressure medicines does not seem to reduce this risk. It’s unknown whether the syndrome or the medications used to treat it are the relevant risk factor.
Advanced kidney disease: Advanced kidney disease, particularly if it requires dialysis, correlates with a higher risk of kidney cancer.
Sickle cell trait and disease: People with either one or two copies of the sickle cell gene are at increased risk of renal medullary carcinoma, a rare form of kidney cancer that often occurs at younger ages, and is more difficult to treat.
Tuberous sclerosis: People with tuberous sclerosis develop tumors in multiple parts of the body, including the kidneys. Kidney tumors associated with this syndrome are usually benign, but may be a form of renal cell carcinoma.
Hepatitis C: Multiple studies have found that hepatitis C increases the risk of kidney cancer. [4][5]
Kidney Stones: Kidney stones are hard deposits of minerals and salts that form in the kidneys. Recurrent kidney stones or complications from kidney stone disease, such as urinary tract infections or obstruction of the urinary tract, can lead to chronic kidney disease (CKD), which is associated with an increased risk of several types of cancers. Large or recurrent kidney stones can cause damage to the kidney tissue, leading to scarring and fibrosis. Chronic kidney damage and inflammation may eventually lead to cancerous changes in kidney cells.
Periodontitis: Periodontal disease is characterized by chronic inflammation of the gums and surrounding tissues, resulting from bacterial infection and immune response. Chronic inflammation is a known risk factor for cancer, as it can promote cellular changes, DNA damage, and abnormal cell proliferation. Systemic inflammation associated with periodontal bone loss may contribute to an increased risk of kidney and pancreatic cancers.
Genetic conditions: About 5-8% of kidney cancers are considered hereditary, and are most often linked to a hereditary cancer syndrome that significantly increases an individual’s cancer risk. These syndromes include: some text
Hereditary leiomyomatosis and renal cell cancer
Birt-Hogg-Dubé syndrome
von Hippel-Lindau disease
Hereditary paraganglioma-pheochromocytoma
BAP1 tumor predisposition syndrome
Cowden syndrome
Hereditary papillary renal cancer
Family history: A family history of kidney cancer, even without a known hereditary cancer syndrome, increases one’s risk of developing kidney cancer. This association is particularly high between siblings.
Long-term use of pain medication: Studies have shown that long-term use of acetaminophen, and possibly aspirin, may increase risk of kidney cancer.
Protective Factors
Several factors have been shown to have protective effects against kidney cancer:
Maintaining a healthy weight: Numerous studies have linked higher BMI to increased risk of various types of cancer, including kidney cancer. Excess body fat can lead to higher levels of estrogen and insulin, as well as increased production of insulin-like growth factors. Higher BMI is also associated with chronic low-level inflammation, which can cause DNA damage over time and contribute to the development of cancer. Maintaining a healthy weight helps you to avoid these risks.
Physical activity: Regular exercise can reduce your risk of several types of cancer through a combination of physiological, hormonal, and immunological changes. It can reduce inflammation, improve immune function, improve hormonal regulation, and lower insulin levels. The American Cancer Society recommends engaging in at least 150 minutes of moderate activity or 75 minutes of vigorous activity each week. Furthermore, data indicates that individuals can see significant incremental benefit with additional exercise.
Water intake: Water intake plays a significant role in maintaining overall health. While the direct impact of increased water intake on kidney cancer is unclear, adequate hydration can improve blood pressure and both reduce risk and improve outlook for chronic kidney diseases, both risk factors for kidney cancer.
Fruit and vegetable consumption: A meta-analysis of 19 studies showed that eating more fruits and vegetables correlates with significantly lower rates of RCC. Fruit and vegetables are rich in various nutrients which have been shown to have protective effects against multiple cancers. These foods contain a variety of antioxidants, which help neutralize free radicals in the body and reduce inflammation.[6]
Screening
Early detection of kidney cancer has a dramatic impact on prognosis. The 5-year survival rate for localized cancer is over 93%, but drops to just 17% once the cancer has spread to distant parts of the body.
Depending on your age and risk factors, the optimal kidney cancer screening will vary:
Urinalysis: This test can detect chemicals, proteins, and red and white blood cells in the urine. Many individuals with kidney cancer will have blood in their urine, even in trace amounts, and other elements of urinalysis can show how well the kidneys and other organs are working. Please note, abnormal results on a urinalysis may indicate several less serious conditions, and should always be interpreted by your doctor.
Urine cytology: This test looks for cancer cells in the urine, a possible indication of kidney cancer. This test is not usually recommended unless imaging tests indicate the possibility of a tumor.
Blood tests: Blood tests don’t currently diagnose kidney cancer directly, but they can highlight imbalances and detect certain chemicals in the blood that might indicate kidney cancer. A complete blood count (CBC) can check for anemia (too few red blood cells), a common symptom of kidney cancer. Polycythemia (too many red blood cells) is a less common indicator. A high neutrophil count–a type of white blood cell–might also be an early sign. Blood chemistry tests can assess overall kidney function and determine whether levels of calcium, lactate dehydrogenase, or liver enzymes are higher than they should be. If blood test results are concerning, they will likely lead to more targeted additional testing.
Imaging tests: CT scans, MRIs, and ultrasounds can all be used to look for kidney cancer, and in some instances, are adequate to diagnose[7] kidney cancer even without a biopsy. Imaging tests aren’t usually recommended unless previous, simpler tests have returned results that indicate the possibility of kidney cancer. If kidney cancer is present, bone scans and x-rays might also be used to determine how far the cancer has spread.
Liquid biopsy: Liquid biopsy is an investigational cancer-detection technique which looks for DNA fragments in the blood to determine whether cancer is present. Though still in its infancy, this technology is promising, particularly in screening for hard-to-detect cancers or cancers whose symptoms are minimal or tend to appear only after they’ve spread. Kidney cancer is one of many cancers which can be screened for via this method.
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