Stages of Wilms tumour

Staging describes or classifies a cancer based on how much cancer there is in the body and where it is when first diagnosed. This is often called the extent of cancer. The healthcare team uses information from tests to find out the size of the tumour, which parts of the organ have cancer, whether the cancer has spread from where it first started and where the cancer has spread. Doctors use the stage to plan treatment and estimate the outcome (prognosis).

The most common staging system in North America for Wilms tumour is the National Wilms Tumor Study Group (NWTSG) staging. This system is based on the results of surgery, looking at the cancer cells under a microscope and whether the cancer has spread within or outside of the kidney. The NWTSG staging system is also used by the Children’s Oncology Group for children with Wilms tumour who are participating in clinical trials.

For Wilms tumour there are 5 stages. Often the stages 1 to 5 are written as the Roman numerals I, II, III, IV and V. Generally, the higher the stage number, the more the cancer has spread.

Doctors may also use the terms local, regional and distant.

Local means within the kidney. It also refers to the staging of the original (primary) tumour, regardless of metastasis. For example, a tumour may be staged as “stage 4 with local stage 3.” This helps to determine which treatment would be best.

Regional means close to or around the kidney.

Distant means in another part of the body, farther from the kidney.

Talk to the doctor if you have questions. Find out more about staging cancer.

The tumour is in one kidney and is completely removed by surgery. The outer layer of the kidney (called the renal capsule) isn’t broken during surgery. The cancer hasn’t spread to major blood vessels in or near the kidney or to the lymph nodes. A biopsy of the tumour wasn’t done before itʼs removed. The cancer hasnʼt spread to distant organs.

About 40% to 45% of Wilms tumours are stage 1.

The tumour was completely removed by surgery. It has grown into the renal sinus (the part of the kidney where it joins the ureter) , and into the fat, soft tissue or blood vessels near the kidney. No biopsy is done before the tumour is completely removed. The cancer hasnʼt spread to the lymph nodes or to distant organs.

About 20% of Wilms tumours are stage 2.

There is still cancer in the abdomen after surgery and at least one of the following is true:

• cancer has spread to the lymph nodes in the abdomen or pelvis
• cancer has spread to or through the peritoneum
• a biopsy of the tumour was done before it was removed
• the tumour broke open before or during surgery
• the tumour was removed in more than one piece
• cancer cells were found at the edges of the area where the tumour was removed (called a positive surgical margin)
• the tumour has grown into nearby vital tissues and organs, so it canʼt be removed completely

The cancer hasnʼt spread to distant organs.

About 20% of Wilms tumours are stage 3.

The cancer has spread to other parts of the body (called distant metastasis), such as to the lungs, liver, brain or bone, or to lymph nodes outside of the abdomen and pelvis.

About 10% of Wilms tumours are stage 4.

The cancer is found in both kidneys at the time of diagnosis. This is called bilateral Wilms tumour.

The cancer in each kidney is also given its own stage.

About 5% of Wilms tumours are stage 5.

Refractory Wilms tumour means that the tumour doesn’t shrink during or after treatment.

Recurrent Wilms tumour means that the cancer has come back after it has been treated.

If it comes back in the same place that the cancer first started, it’s called local recurrence.

If it comes back in tissues or lymph nodes close to where it first started, it’s called regional recurrence.

It can also recur in another part of the body. This is called distant metastasis or distant recurrence.