Kidney cancer (renal cell carcinoma)

A kidney cancer is based on malignant changes in kidney cells. If the cancer develops from different cells of the kidney tissue, this is called renal cell carcinoma. Renal cell carcinoma is the most common type of kidney tumor in adults, accounting for more than 80 percent of cases. Generally speaking, however, renal cell carcinomas are quite rare, accounting for only about three percent of all cancer cases.

The remaining types of kidney cancer develop from the urinary tract or from lymphatic tissue. It is also possible that kidney tumours are metastases (daughter tumours) of other cancers in the body.

In Germany, there are more than 6,500 new cases in women and more than 10,000 new cases in men every year. The incidence of the disease increases sharply with age - the average age of onset is 67 for men and 71 for women.

The exact causes for the development of a kidney tumor are largely unknown. However, smoking, obesity, alcohol consumption, renal insufficiency (chronic kidney weakness) and kidney cysts are considered risk factors. Rarely, renal cell carcinoma can also be the result of genetic changes. It is not clear whether chronic exposure to substances such as cadmium can promote the development of kidney cancer.

In most cases, the renal tumour is localised at the lower pole of one kidney in the renal cortex and proliferates towards the renal pelvis. Very rarely, both kidneys are affected by a tumor.

Renal cell carcinomas tend to spread at a relatively early stage via the lymphatic as well as blood vessels and to form daughter tumours (metastases). Metastases frequently affect the lymph nodes, bones, lungs, liver and brain. Metastases in the other kidney are also possible.

According to experts, the best way to prevent the development of renal cell carcinoma is to stop smoking and maintain a normal body weight.

Initially, renal cell carcinoma goes unnoticed in the vast majority of cases. Only later can the disease become noticeable - the following complaints and symptoms can be signs of a kidney tumour:

• Haematuria (blood in the urine)
• Flank pain (pain in the area of the back)
• Sudden weight loss
• Anemia (lack of blood)
• New onset hypertension (high blood pressure)
• Palpable tumor in the abdomen
• Deteriorated liver function values
• Hypercalcemia (increased calcium levels in the blood)
• Fever
• Changes in blood pressure

Over half of all kidney cancer diagnoses are made by chance during ultrasound examinations of the abdomen.

Normally, renal cell carcinoma cannot be detected by a doctor during a physical examination. However, in rare cases, there may be evidence of a cancerous growth in the kidney. Examples of this would be:

• Palpable resistance on examination of the abdominal region.
• Enlarged lymph nodes in the neck area.
• Water retention in the testicle (called a hydrocele) that does not resolve when the testicle is elevated.
• Pronounced edema (water retention) in the legs.

However, these signs usually indicate other diseases and only occur in exceptional cases of kidney cancer. A blood test can be used to determine any effects of renal cell carcinoma on the body's metabolism.

The most important procedures for the final diagnosis of a kidney tumour are computer tomography (CT) and ultrasound examination of the abdomen. An X-ray contrast agent is usually administered before the CT is performed.

If the kidney tumour is to be treated surgically, a CT or an MRI (magnetic resonance imaging) must be performed in any case in order to enable optimal planning of the operation. In addition, the degree of spread of the renal cell carcinoma and possible metastases (daughter tumours) can be detected with the help of these imaging procedures.

If metastases are suspected, an X-ray examination, a CT of the chest, a CT of the head and a scintigraphy of the bones can also be performed. In very rare cases, angiography (imaging of the blood vessels using X-rays and contrast medium) of the renal arteries is also necessary. Fine needle biopsy (removal and examination of a tissue sample) of the kidney tissue is also only performed in exceptional cases.

Different treatment approaches are available to treat renal cell carcinoma:

Surgery

Even today, the only treatment that can lead to a cure for the cancer is the complete removal of the kidney affected by the cancer and, in certain cases, the surrounding lymph nodes. In addition, removal of the adrenal gland may be necessary. Rarely can kidney cancer be surgically removed while preserving the function of the kidney.

Especially in people without metastases, surgical removal of the tumor is the treatment of choice. However, surgery may also be performed in patients with metastases, for example to relieve pain or to increase the chances of success of other treatments.

Drug therapy

Several different drugs are available to treat kidney cancer. The effect is often to affect the metabolism of the cancer cells (for example, blood supply, nutrient supply) and thereby prevent the cancer from progressing. Examples would be:

• Tyrosine kinase inhibitors (for example, sunitinib).
• mTor inhibitors (for example temsirolimus)
• Immunotherapy with interleukin-2 and interferon-alpha (leads to activation of the immune system, which should slow down the growth of the tumour)
• Monoclonal antibodies (for example bevacizumab)

Different treatment methods are often used in combination to achieve the best possible chances of success.

Radiation / chemotherapy

In certain cases - such as distant metastases in the brain or in the bones - radiation therapy can be administered to alleviate the symptoms of the disease. Chemotherapy is not successful with renal cell carcinoma.

The prognosis of kidney cancer depends largely on the time of diagnosis. The later the cancer is discovered, the larger the tumor and the higher the risk of metastases. With the help of ultrasound examinations, many renal cell carcinomas can nowadays be diagnosed at a very early stage. The five-year survival rate (number of living patients five years after diagnosis) is about 65 percent.

In the case of kidney problems such as discoloured urine or unexplained flank pain, it is advisable to consult a doctor in good time so that a possible tumour can be detected in good time. In addition, the risk of disease can be significantly reduced by abstaining from nicotine and alcohol and avoiding increased body weight.