How is kidney cancer diagnosed?
In the past, kidney cancer was diagnosed only after the tumors had become quite large and caused symptoms (flank pain, blood in the urine). Today, most kidney tumors are found incidentally during imaging studies such as ultrasound, CT scan or MRI.
While some small tumors are destined to stay small and not cause harm, others can have aggressive behavior and earlier detection improves outcome. Tumors that have grown large or spread (metastasized) to other parts of the body are more difficult to treat and present an increased risk for death.
Staging of Kidney Cancer
In addition to taking a complete medical history, performing a physical exam, and obtaining laboratory tests, your physician may order various imaging tests. These studies are to characterize the kidney tumor and evaluate if the cancer has spread outside of the kidney (metastasized).
- Chest X-ray. Evaluation of the chest for any lung involvement.
- Ultrasound Examination. Uses high-frequency sound waves to generate images of your internal organs, such as your kidneys.
- Computerized Tomography (CT) or Magnetic Resonance Imaging (MRI) scan. CT scans use computers for focused X-rays to create a detailed image. MRI scans use magnetic fields and radio waves to generate cross-sectional pictures of your body.
- Bone Scan. Uses a very small amount of a radioactive substance with imaging to detect bone involvement.
- Sestamibi Spect/CT Scan. Nuclear medicine scan to detect less aggressive renal tumors. This is being offered on a research protocol to determine if this aids decision making.
- PET/CT Scan. Uses special dye containing radioactive tracers with a CT scan (only utilized in select cases).
Staging Factors of Kidney Cancer
The most important factor in predicting prognosis, as well as the treatment options, is the "stage" or extent of the cancer. Staging is the process of gathering information from physical examinations and diagnostic tests to determine the size and location of the tumor and how widespread a cancer is. Important Staging Factors in Kidney Cancer are:
- Tumor size
- Spread to tissues surrounding the kidney (fat and vein)
- Spread to contiguous organs (organs next to the kidney)
- Spread to nearby lymph nodes (the lymphatic filtration system)
- Spread to other organs like lung, bone, liver (distant metastasis)
Common staging systems for Kidney Cancer
- The TNM System
- The AJCC System (Combining the various TNM Factors)
- The University of California, Los Angeles Integrated Staging System (UISS)
Fuhrman grading system for Kidney Cancer
Another important factor used by doctors in assessing renal cell carcinoma is its Fuhrman grade (named after the pathologist who developed the system). This refers to how closely the cancer cells look like normal kidney cells under a microscope.
The Fuhrman grading system ranks tumor cells on a scale of 1 through 4.
Grade 1 tumor cells don't look very different from normal kidney cells. Grade 1 cancers typically grow and spread slowly and most often have a good prognosis. On the other hand, Grade 4 tumor cells look quite different from normal kidney cells and have a worse prognosis.
The most commonly used staging system is that of the American Joint Committee on Cancer (AJCC), also known as the TNM Staging System. The TNM (tumor-node-metastasis) system uses stages generally similar to those of the Robson system and is becoming more widely accepted because it provides a more detailed description of the tumor(s).
- The letter T followed by a number from 0 to 4 describes the tumor's size and spread to nearby tissues. Some of these numbers are further subdivided with letters, such as T1a and T1b. Higher T numbers indicate a larger tumor and/or more extensive spread to tissues near the kidney.
- The letter N followed by a number from 0 to 2 indicates whether the cancer has spread to lymph nodes near the kidney and, if so, how many are affected. Lymph nodes are bean-sized collections of immune system cells that help the body to fight infections and cancers.
- The letter M followed by a 0 or 1 indicates whether or not the cancer has spread (metastasized) to other organs such as the lungs or bones, or to lymph nodes that are not near to the kidneys.
The UCLA Integrated Staging System (UISS), developed by translational researchers within the UCLA Department of Urology, is a more complex but probably more accurate system that incorporates the TNM staging systems, a person's overall health and the Fuhrman grade of the tumor.
In the UISS system: Patients without any tumor spread are divided into three groups: low risk, intermediate risk and high risk.
- The Low Risk group is considered Stage I; are in excellent health other than the cancer and have a low Fuhrman grade tumor.
- The Intermediate Risk group is all others, without any spread.
- The High Risk group is either Stage III (but without lymph node spread), in poor health and have a high Fuhrman grade score; or Stage IV (without any spread, T4, N0, M0).
The most recent five-year cancer-specific survival data for the low risk group is 91%, for the intermediate risk group is 80%, and for the high risk group is 55%.
Patients with tumor spread, to lymph nodes or distance sites such as bone, lung or liver, are also divided into these three groups. Low risk patients have a tumor that is T1-3, N1, M0. High risk patients have a T4 tumor, poor health and high Fuhrman grade or distant spread. Intermediate grades are all others. The five-year cancer-specific survival is lower in these people whose tumors have spread: for the low risk group it is 32%, for the intermediate risk group 20% and for the high risk group 0%.