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Renal cell carcinoma

Renal cell carcinoma: Description

Malignant renal (kidney) tumors encompass tumors with various forms of cell proliferation that - statistically speaking - are relatively rare, representing 2 percent of all cancers. The most common type among them is renal cell carcinoma (also: hypernephroma, Grawitz tumor, renal adenocarcinoma) which originates in the cells of the uriniferous tubules. A distinction must be made between so-called clear cell, papillary, chromophobe and the very rare Bellini duct carcinoma. The latter cancer is a particularly aggressive, rapidly spreading form with a generally poor prognosis.

Distinct from renal cell carcinoma are malignant tumors of the urinary tract (urothelial carcinoma) that attack the pyelocaliceal system and are then called renal pelvis carcinoma. Occasionally, metastases from other malignant tumors (e.g. lung, breast or skin cancer) may appear in the kidneys.

Due to the strong blood flow through the kidneys, tumor cells can under certain circumstances enter the organism through the blood and lymph vessel systems relatively quickly, thus causing the formation of metastases or distant metastases, especially in the bones and the lungs, or more rarely in the brain or liver.

Renal cell carcinoma: Symptoms

In its early stages the disease often causes no clinical symptoms, so that the tumor is sometimes discovered too late. A possible sign of a kidney tumor is visible amounts of blood in the urine, referred to as hematuria (whereas low, non-visible levels are called microhematuria). In advanced stages, flank pain and a hardening that can be felt by palpation can occur. At this point the renal cell carcinoma may already spread to the adrenal glands and adjacent fat tissue. Additionally, in advanced stages symptoms such as fever, night sweats, loss of appetite, involuntary weight loss, nausea, increased blood pressure and anemia may occur.

Renal cell carcinoma: Causes and Risks

The causes of the onset of a kidney tumor are largely unknown, but certain factors may favor and provoke it. This includes nicotine and alcohol consumption, obesity, lack of hydration or abuse of drugs, especially painkillers. Secondary diseases such as hypertension, chronic renal failure, cystic kidney disease or genetic diseases such as tuberous sclerosis and von Hippel-Lindau disease are also considered risk factors.

As with many cancers, increasing age and a genetic predisposition for the development of kidney cancer may increase the risk.

Renal cell carcinoma: Examination and Diagnosis

Today about 70 percent of all kidney tumors are discovered accidentally in the context of other tests (e.g. sonography). A thorough physical examination can provide initial indications of advanced kidney cancer: especially suspicious are a palpable resistance in the abdomen, enlarged lymph nodes in the neck, or edematous (swollen) legs. For further evaluation, in addition to laboratory tests, use of imaging methods such as sonography (ultrasound), computed tomography (CT) or magnetic resonance imaging (MRI) is necessary. If bone metastases are suspected, skeletal scintigraphy is performed. A tissue sample (biopsy) to confirm the diagnosis of renal cell carcinoma is necessary only in special cases. If the imaging findings are clear and unambiguous, the probability of a malignant tumor is over 80 percent, so that treatment can be initiated without further measures. Even with a fine needle biopsy there is always a certain risk of bleeding in the kidney, and also - theoretically at least - tumor cells could be transferred via the biopsy.

Renal cell carcinoma: Treatment

Crucial in the choice of treatment is the stage of the tumor. Surgical removal of the tumor is still considered to be the most effective treatment method, regardless of whether the kidney is completely (entire kidney and possibly the adrenal gland) removed or if a conservative kidney-preserving operation is performed. In the organ-preserving operation only the tumor itself (with a certain safety margin) is removed from the kidney. Today it should always be possible to operate on tumors up to a size of 4.0 cm this way. Depending on the location and size, this is also technically feasible in some cases even for larger tumors. In patients with a genetic disease (e.g. von Hippel-Lindau) organ preservation should always be pursued, even if in some cases more than 10 tumors must be removed from a kidney during the operation. This can of course only be undertaken in highly specialized medical centers.

In cases of individual metastases (e.g. in the lungs) a complete surgical removal should, if technically possible, also be sought.

Today, various drugs that act on tumor cell metabolism are used in advanced metastatic stages of renal cell carcinoma. These include tyrosine kinase inhibitors (TKI), sunitinib, sorafenib or pazopanib. Alternatively, antibodies (e.g. bevacizumab) can be used, which inhibit neovascularization (angiogenesis) of the tumor. Another group of drugs affects the mTOR pathway (temsirolismus, everolimus). According to clinical trials, these are especially suited for poorly differentiated, aggressive renal cell carcinoma. In the past a special form of immunotherapy was used in which the substances alpha interferon and/or interleukin-2 were given in order to stimulate the immune system and enable it to eliminate the cancer cells independently. All medicinally systemic therapies for metastatic renal cell carcinoma take in principal a merely palliative approach, i.e. they can extend the patient's life - in some cases significantly - but unfortunately cannot cure the disease. Therefore, quality of life and possible negative side effects play a very important role in such treatment.

Radiation therapy is usually used palliatively in renal tumors that have already metastatized, and helps to alleviate the symptoms, particularly if there are bone metastases, which without treatment can otherwise cause severe pain, or in the worst case pathological fractures. For tumor embolization there is also a palliative method: by closing the renal artery with a catheter, the tumor can no longer be supplied with the blood, and in some circumstances may spontaneously regress.

With radio-frequency ablation (RFA) the situation is different. Here, using image monitoring (usually computed tomography) a probe is inserted into the tumor, which is then heated to about 100 degrees Celcius. All the tumor cells can thereby be destroyed. There are already large scientific data series for liver tumor treatment using this minimally invasive procedure. For kidney tumors it is still a relatively new procedure, meaning the long-term data must first be obtained.

Unfortunately, the chemotherapy sometimes used very successfully to treat other malignant tumors is much less effective with kidney tumors. This is due to the already existing primary resistance of the tumor cells (multidrug resistance or MDR).

Renal cell carcinoma: Course and Prognosis

The prognosis for kidney tumors is very individual and depends on the size, growth mode, stage and possible metastasis of the tumor. If small tumors are discovered at an early stage, the prognosis today is very good.

A complete cure is possible only in case of surgical removal. This also applies in cases of single metastases (e.g. in the lung).

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