What Are Some Facts About Kidney Cancer?



The most common kidney cancer is called Renal Cell Carcinoma (RCC). Worldwide, over 100,000 people die of RCC each year. Renal cell carcinoma is the seventh most common cancer and tenth most common cause of cancer-related deaths among men. Overall, approximately 2-3% of all cancers are Renal Cell Carcinomas. Renal Cell Carcinomas make up 80 - 85% of all primary renal cancer in adults.

Males were previously thought to have been twice as likely to develop RCC as females, however this gap is narrowing.

The number of cases of RCC being diagnosed is increasing by approximately 2% per year. This may be because many RCCs are now diagnosed by coincidence when someone has scans (such as ultrasounds or CT scan) performed for other reasons. It is possible that because such scans are becoming more common, more RCC is being diagnosed, and at an earlier stage. The average size of RCCs at diagnosis is decreasing. The number of deaths due to RCC are also decreasing.

In the United States, 2 percent of all cancers arise from the kidney. Each year, kidney cancer is diagnosed in approximately 38,000 Americans and is the cause of death in nearly 12,000 Americans. Kidney cancer is still slightly more common in males and is usually diagnosed between the ages of 50 and 70 years.

In Australia, there are just over 2,000 new cases of primary kidney cancer diagnosed each year. Australians have a 1 in 74 risk of developing RCC during their lifetime. Kidney cancer caused 855 deaths in Australia in 2007 (539 men, 316 women), accounting for 0.6% of all deaths.

Primary kidney cancer is mostly a disease seen in adults over 40. The average age of people found to have Renal Cell Carcinoma is 55 years. Renal Cell Carcinoma is rare in children.

What Are The Symptoms For Kidney Cancer?

Many kidney tumours do not produce symptoms, but may be detected incidentally during the evaluation of an unrelated problem or during routine screening for people who are in high-risk categories. Compression, stretching and invasion of structures near the kidney may cause pain in the flank, abdomen or back, palpable mass and blood in the urine either microscopic or grossly visible. The classic triad of RCC of flank pain, hematuria and a palpable abdominal renal mass, occurs in less than 10% of current patients. If cancer spreads beyond the kidney, symptoms depend upon the involved organ. Shortness of breath or coughing up blood may occur when cancer is in the lung, bone pain or fracture may occur when cancer is in the bone and neurolic symptoms may occur when cancer is in the brain. In some cases, the cancer causes associated clinical or laboratory abnormalities called paraneoplastic syndromes. These syndromes are observed in approximately 20 percent of patients with kidney cancer and can occur in any stage, including cancers confined to the kidney. Symptoms from paraneoplastic syndromes include weight loss, loss of appetite, fever, sweats and high blood pressure. Laboratory findings include elevated red blood cell sedimentation rate, low blood count (anemia), high calcium level in the blood, abnormal liver function tests, elevated alkaline phosphatase in the blood, and high blood count. In many cases, the paraneoplastic syndrome resolves after the cancer is removed.

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What Is A Kidney Tumour?

A kidney tumour is an abnormal growth within the kidney. The terms "mass", "lesion" and "tumour" are often used interchangeably. Tumours may be benign (non-cancerous) or malignant (cancerous). The most common kidney lesion is a fluid-filled area called a cyst. Simple cysts are benign and have a typical appearance on imaging studies. They do not progress to cancer and usually require no follow-up or treatment. Solid kidney tumours can be benign, but are cancerous more than 90 percent of the time.

Renal Cell Carcinoma (RCC)

Renal Cell Carcinoma is the most common form of cancer that originates in the kidney. Cancers that have started to grow in a particular location and have not spread there from somewhere else, are known as primary cancers. Cancers that have spread to somewhere else are known as secondary cancers or metastases. Renal is a technical word referring to the kidney. Carcinomas are cancers that grow from cells that line body organs (epithelial cells). RCC occurs due to mutations (abnormalities) of cells in the kidney's filtering system. RCCs make up 80-85% of primary kidney cancer. Renal cell cancer is the most common type of kidney cancer in adults. Renal cell cancer is also called renal adenocarcinoma or hypernephroma. In renal cell cancer the cancerous cells are found in the lining of the tubules, the smallest tubes inside the nephrons that help filter the blood and make urine.

Kidney cancer can be classified into several different types based on the appearance of the cancer cells under a microscope (this is called the microscopic appearance or microscopy), and other genetic factors. There are several types of renal cell cancer that can be identified by looking at the cancer cells under a microscope. The main ones are:

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Other rarer types of kidney cancer include:

Often kidney cancers contain more than one of these cell types. Knowing the type of renal cancer will help your doctors to make the most appropriate decision about treatment options.

As always, data is never up to date, but visiting State Cancer Profiles (USA)

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There are also statistics avaiable for Australians, with the following Excel tables available:

This report presents detailed projections of cancer incidence for major cancers. The report provides projections of both incidence rates and expected numbers of new cases by age and sex for 60 cancers and groups of cancers. The projections in this report are based on trends in national cancer incidence data from 1982 to 2001 held by the AIHW in the National Cancer Statistics Clearing House. The projections in this report were commissioned by the National Cancer Strategies Group to support planning of cancer services and this report is an important reference for all those interested in the prevention, detection, treatment and management of cancer in Australia. Cancer incidence projections Australia 2002 to 2011.

Predisposing Factors

RCC is linked to a number of risk factors. These include:

1. Cigarette smoking, which is the most important risk factor. It doubles the likelihood of developing RCC and may be associated with up to one third of all cases;
2. Acquired cystic kidney disease: dialysis patients (who require a machine to filter their blood, because their kidneys do not work well enough) who develop polycystic disease of the kidneys appear to be most at risk for RCC. The estimated risk of RCC amongst this group is 30 times greater than the general population. Acquired cystic disease develops in approximately 35 to 50% of chronic dialysis patients. Around 6% of these eventually develop RCC, commonly with multiple tumours in both kidneys. Men (ratio 7:1) and people with large cysts in large kidneys appear to be at significantly increased risk of developing kidney cancer, which tends to occur after 8-10 years of dialysis;
3. Obesity, which is being very overweight, appears to be associated with an increased risk of developing RCC in both men and women;
4. High blood pressure, also known as hypertension, has been found to be a risk factor for RCC, independently to obesity and smoking;
5. Occupational exposures to toxic compounds: risk of RCC is increased in workers exposed to asbestos, cadmium, petroleum products, dry-cleaning solvents, as well as those who work in the iron and steel industries;
6. Genetic predisposition: several genetic syndromes have been associated with an increased risk of RCC. These include von-Hippel Lindau (VHL) syndrome, hereditary papillary renal cancer, hereditary leiomyoma RCC syndrome, and Birt-Hogg-Dube syndrome;
7. Unopposed oestrogen therapy: One study found that women who have more than 5 children are at increased risk of developing RCC. Use of the combined oral contraceptive pill was associated with a slightly reduced risk of RCC;
8. Analgesic abuse nephropathy: individuals who use aspirin or phenacetin contained within analgesics (painkillers) over a long period are at risk of developing chronic renal failure. In addition to kidney failure, they may also be at an increased risk of RCC;
9. Childhood chemotherapy: Chemotherapy given during childhood to treat cancer, autoimmune disorders, or for bone marrow transplantation has been associated with increased risk of RCC (translocation carcinoma as discussed above) because of genetic abnormalities caused by the treatment; and
10. Previous radiation therapy: Renal cell carcinoma caused by radiation occurs in less than 1% of cases of RCC, and in one study it occurred 25-35 years after radiation therapy.

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Screening

Due to the fact that RCC is uncommon in the general population, screening of people who have no symptoms of RCC is generally not recommended. People at high risk for development of RCC may be monitored with abdominal ultrasound, CT, or MRI.

Those who may benefit from screening for RCC include:

Renal Cysts

One thing an ultrasound can "see" better than other types of scans is what's inside a lesion. This is why the ultrasound is handy for determining if something is solid or cystic, and what sort of a cyst it is.

If it is fluid inside with no dividing walls, and if the outside wall is thin, smooth, and spherical or oval, then it's a simple cyst and benign -- nothing to worry about. If it is filled with fluid divided up by walls (septations), then it is a complex cyst and quite possibly cancerous. The degree of complexity of the internal structure and the makeup of the external walls can be rated using the Bosniak Scale.

Some renal cancers stem from cystic like structures. While rare there is a cystic RCC.

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