Kidney cancer

Introduction and incidence

The kidney is a paired organ that filters blood and produces urine, which is used to excrete harmful substances from the body. Urine from the kidney passes through the ureter into the bladder and then out of the body through urination. Kidney cancer is slightly more common in men. According to data from the Croatian Cancer Registry from 2017, it accounted for about 5% of all new cancer cases in men and about 3% in women. There are several types of kidney cancer, the most common of which is renal cell carcinoma, which accounts for about 85% of all cases (other types are urothelial carcinoma, sarcoma, lymphoma and Wilms' tumor, which occurs primarily in children).

​Risk factors

Risk factors for the development of kidney cancer include smoking, obesity, high blood pressure, kidney cancer in the family and some genetic syndromes (for example, von Hippel-Lindau disease or hereditary papillary renal cell carcinoma). There is evidence that long-term uncontrolled use of some over-the-counter painkillers may also increase the risk. You can read more about risk factors for developing cancer in a separate article.

​Signs and symptoms

Early kidney cancer often has no symptoms. As the disease progresses, blood in the urine, a lump in the abdomen, pain on one side of the abdomen that does not go away, loss of appetite and weight loss, and anemia may occur. If any of these symptoms persist for a long time, you should definitely seek medical advice.

Figure 1. Stage III kidney cancer. The tumor has spread to the renal vein and possibly to nearby lymph nodes. Treatment is surgical. (Source: Wikimedia commons)

Diagnosis

The basis is a detailed examination of the patient and a thorough medical history. Ultrasound, CT or MRI of the abdomen are used as imaging tests. In practice, CT is most often used, which is widely available and provides satisfactory imaging accuracy, and can raise a thorough suspicion of kidney cancer. Blood and urine analysis are often performed, while there are no reliable tumor markers for kidney cancer. The definitive diagnosis of the disease is made by biopsy of the tumor, or by surgery to completely remove it.​ After the disease is confirmed, additional tests may be ordered to assess the possible spread of the disease, such as a chest CT scan (suspected lung metastases) or bone scintigraphy (suspected bone metastases). You can read more about cancer diagnostics in a separate article.

Treatment

Kidney cancer is treated depending on the type of tumor, the patient's general condition and the stage of the disease. Surgical treatment is used in most patients, even some with metastatic disease, which makes kidney cancer treatment specific. Depending on the individual patient, only the tumor tissue and a small part of the surrounding healthy tissue can be removed (partial nephrectomy), the removal of the entire kidney affected by the tumor (simple nephrectomy) or the removal of the adrenal gland and surrounding tissue (radical nephrectomy). The surgical approach depends, among other things, on the function of the second kidney, because if the patient has no kidneys or they are not functional, lifelong dialysis is required. Therefore, for example, in patients who have cancer of one kidney, and the other has impaired function for some reason, a partial nephrectomy can be considered in order to maintain the function of the remaining kidney tissue. In patients with a healthy second kidney, the main treatment option is radical nephrectomy. The role of radiotherapy in kidney cancer is relatively limited, and it is most often used in metastatic disease as a palliative method (eg radiation of painful bone metastases). The same is true with chemotherapy, and apart from surgery, the main forms of kidney cancer treatment today are targeted therapy and immunotherapy, separately or in combination. Targeted therapies include monoclonal antibodies (e.g. vascular endothelial growth factor inhibitor bevacizumab), tyrosine kinase inhibitors (sunitinib, pazopanib, cabozantinib, axitinib, sorafenib...) and mTOR inhibitors (everolimus, temsirolimus...). Most of these smart drugs, among other effects, work by preventing the formation of new blood vessels that are necessary for tumor growth. Immunotherapy also includes several groups of drugs that are effective in kidney cancer, such as the CTLA-4 inhibitor ipilimumab; the PD-1 inhibitors nivolumab, pembrolizumab and avelumab; interferons; interleukin-2.

In kidney-limited disease, the best treatment option is always surgery, regardless of the size and stage of the primary tumor, and some patients are cured by surgery. In high-risk patients, adjuvant (postoperative) treatment can be performed after surgery to reduce the risk of disease recurrence, with immunotherapy being particularly important. Further research is underway.

In metastatic disease, systemic treatment is the mainstay. This usually involves targeted therapy and/or immunotherapy, and there are several lines of treatment. This fourth stage of the disease is usually incurable, and the goal of therapy is to prolong survival and maintain or improve quality of life. Patients also have the option of enrolling in clinical trials for treatment with new experimental drugs.

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