Renal cell carcinoma is the most common type of adult kidney cancer. The kidneys are two bean-shaped organs located behind the abdominal organs, with a primary role of filtering waste from the blood into urine. They also produce hormones that regulate blood pressure and red blood cell production. Renal cell carcinoma originates in the lining of the kidney’s small filtering tubes when cells grow uncontrollably and form a mass, or tumor.
Causes and Risk Factors
The exact cause of renal cell carcinoma (RCC) is unclear, but several risk factors have been identified. Smoking tobacco increases the risk, particularly with long-term use. Obesity also elevates the risk, potentially due to hormonal and metabolic changes, as does high blood pressure (hypertension).
Certain pre-existing medical conditions can predispose an individual to this cancer. People with advanced kidney disease, especially those requiring long-term dialysis, have a higher risk. Workplace exposure to substances like cadmium, asbestos, and some organic solvents can also contribute to RCC development.
Genetic predisposition accounts for a small percentage of cases. A family history of kidney cancer increases risk, even without a known inherited syndrome. Specific hereditary conditions that raise the risk include von Hippel-Lindau disease, hereditary papillary renal cell carcinoma, and Birt-Hogg-Dubé syndrome, which all stem from specific gene mutations.
Signs and Symptoms
In its early stages, renal cell carcinoma often produces no noticeable symptoms. As a result, many kidney tumors are discovered incidentally during imaging tests, such as CT scans or ultrasounds, performed for unrelated medical reasons. These incidentally found cancers are often smaller and at an earlier stage.
As a tumor grows, it may cause more distinct signs. The classic triad of symptoms includes hematuria (blood in the urine), persistent pain in the flank or lower back, and a palpable mass in the abdomen. Hematuria can make the urine appear pink, red, or cola-colored, but this combination of symptoms is now seen in a small percentage of patients and often indicates advanced disease.
Other less specific symptoms can arise from the body’s reaction to the cancer, known as paraneoplastic syndromes. These can include unexplained weight loss, persistent fever, and chronic fatigue. The cancer can also lead to high blood pressure, an elevated red blood cell count, or high blood calcium levels, requiring a medical evaluation to determine the cause.
Diagnosis and Staging
Diagnosis begins with a physical exam and lab tests, but imaging is the primary method for identifying a kidney tumor. CT scans and MRI provide detailed images showing the mass’s size, shape, and location. An ultrasound may also be used to determine if a mass is solid or a fluid-filled cyst.
Often, the appearance of the mass on imaging is enough to diagnose RCC. However, a biopsy may be performed to obtain a tissue sample for microscopic examination. A biopsy is useful when imaging is inconclusive or if non-surgical treatment is considered, as it confirms the cancer type and its aggressiveness.
Once diagnosed, the cancer is staged to describe its extent. Staging determines the tumor’s size and whether it has spread beyond the kidney, and is used to determine the treatment plan.
- Stage I: The tumor is small (less than 7 cm) and confined to the kidney.
- Stage II: The tumor is larger than 7 cm but still confined to the kidney.
- Stage III: The tumor has grown into major veins or nearby tissues or has spread to nearby lymph nodes.
- Stage IV: The cancer has metastasized to distant organs like the lungs, bones, or brain.
Treatment Approaches
Treatment for renal cell carcinoma depends on the cancer’s stage and the patient’s health. For localized cancer, surgery is the primary treatment with the goal of a cure. A radical nephrectomy involves removing the entire kidney, the attached adrenal gland, and surrounding fatty tissue. For smaller tumors, a partial nephrectomy may be performed, where only the tumor and a small margin of healthy tissue are removed, preserving kidney function.
For patients who are not candidates for surgery, less invasive techniques are available for small tumors. Cryoablation uses extreme cold to destroy cancer cells, while radiofrequency ablation uses high-energy radio waves to kill the tumor. These methods are delivered via a needle-like probe inserted through the skin, guided by imaging. While effective for small masses, surgery is considered the most effective treatment for localized RCC.
When the cancer is advanced or has metastasized, treatment shifts to systemic therapies. Traditional chemotherapy is not effective against RCC, so treatment relies on targeted therapy and immunotherapy. Targeted therapy drugs interfere with molecules that fuel cancer growth and the blood vessels that feed tumors.
Immunotherapy harnesses the body’s immune system to fight the cancer. Immune checkpoint inhibitors are drugs that block proteins on immune cells, allowing the immune system to better attack cancer cells. These systemic treatments are often used in combination to improve outcomes for patients with metastatic RCC.
Prognosis and Survival Rates
The prognosis for renal cell carcinoma is influenced by several factors, with the cancer’s stage at diagnosis being the most significant. Other factors include the tumor’s grade (how aggressive the cells appear), the RCC subtype, and the patient’s overall health and age. Cancers detected at an earlier, localized stage have a much better prognosis than those that have spread.
To provide a general outlook, doctors refer to 5-year relative survival rates. This statistic compares people with the same type and stage of cancer to the general population. For example, a 90% 5-year relative survival rate means that people with that cancer are, on average, 90% as likely as people without the cancer to live for at least five years after diagnosis.
For localized RCC (Stage I), the 5-year survival rate is around 93%. When the cancer has spread to nearby structures or lymph nodes (Stage III), the rate is approximately 75%. For distant or metastatic cancer (Stage IV), the survival rate drops to around 15-18%. It is important to remember that these are statistical averages, and an individual’s outcome can vary based on their circumstances and response to treatment.