Kidney cancer (or renal cancer) is a type of cancer in which the cells of the kidney start to multiply excessively. Kidneys are a pair of bean-shaped organs approximately the size of a fist. They are located below the rib cage on each side of the spine and are tasked with filtering the blood to remove the wastes.

Kidney cancer can be of 4 types:

• Renal cell carcinoma (RCC): It is the most common type of cancer accounting for approximately 90% of cases of kidney cancer.

• Urothelial carcinoma (or transitional cell carcinoma): It begins in the part of the body that connects the kidney and the bladder.

• Wilm’s tumor: A very rare form of kidney cancer mostly found in children.

• Renal sarcoma: It is the least common type of kidney tumor. It originates in the connective tissue around the kidneys. 

Symptoms

Kidney cancer does not present with symptoms in its early stages. The common symptoms in the late stages are:

• Blood in urine (hematuria)

• Pain in the back or side of the body

• Loss of appetite

• Unexplained weight loss

• Anemia (lower-than-normal amount of healthy red blood cells)

• High blood pressure

• Tiredness

• Low-grade fever

Diagnosis

The major components of a diagnostic workup are a medical history review, physical examination, and blood and urine tests.

• Urine test: A urine sample is tested for various parameters along with the presence of blood. Very minute amounts of blood that cannot be seen through the naked eye can be detected in this test. 

• Blood test: It is performed to measure the levels of various types of blood cells, electrolytes, and proteins (creatinine) in the blood.  High creatinine level in the blood indicates poor kidney function. 

• Imaging tests: A variety of imaging tests, such as computed tomography (CT), magnetic resonance imaging (MRI), and ultrasonography are utilized in the diagnosis of kidney cancer. They help identify the presence and location of abnormal masses in the kidney. 

• Histopathological examination of the biopsy specimen: A small section of the tissues in the kidney is removed using invasive methods and tested under a microscope (histopathological examination) for the presence of a tumor. This tissue sample is also tested for genetic testing as a basis for targeted therapy.

Management

The treatment options for kidney cancer comprise surgical removal of the tumor, targeted therapy, immunotherapy, and sometimes radiation therapy.

Surgery: The most common first-line therapy for kidney cancer is the surgical removal of the cancer mass. The decision on the part of the kidney to be removed depends on the spread of the tumor and the general health status of the patient.

Usually, surgical options are divided into the following categories based on the extent of kidney tissue removed:

• Nephrectomy: This involves the removal of the entire kidney along with the draining lymph nodes. In almost all patients, cancer is restricted to only one kidney. Therefore, the removal of a cancerous kidney is often a curative therapy. However, it increases the risk of kidney disease and the need for dialysis.

• Partial nephrectomy: It is a kidney-sparing option in which only the cancer and a small portion of surrounding healthy tissue are removed. It reduces the risk of complications but the cancer can come back (recurrence) following partial nephrectomy.

Targeted therapy and immunotherapy: Targeted therapy drugs work against only the specific features found in the cancer cell. Thus, they only target the cancer cells; sparing the healthy cells of the body. Immunotherapy uses the body’s immune system to fight the cancer. Targeted therapy and immunotherapy are relatively newer classes of drugs for cancer treatment.

In kidney cancer, these drugs are used when the cancer is spread to other parts of the body that cannot be easily removed through surgery.

Radiation therapy: It destroys the cancer cells through powerful beams of radiation directed at the cancer from outside the body. It is used in cases when the cancer has spread to other parts of the body such as the brain and bones.

While kidney cancer can often be cured if caught early, it can impact the quality of life due to the potential loss of kidney function and the spread of cancer to other parts of the body. Ongoing research aims to better understand the molecular basis of kidney cancer to develop more targeted and less toxic therapies.