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. Information from tests is used 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. Your healthcare team uses the stage to plan treatment and estimate the outcome (your 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. 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. Talk to your doctor if you have questions about staging.

When describing the stage, doctors look at where the tumour is in the kidney. They also look to see if there are cancer cells at the edges of the tissue (called margins) removed by surgery. If cancer cells are not found, it is called negative surgical margins. If cancer cells are found, it is called positive surgical margins. Doctors may also use the terms local, regional and distant. Local means within the kidney. Regional means close to or around the kidney. Distant means in another part of the body farther from the kidney.

Find out more about staging cancer.

The tumour is in 1 kidney and it was completely removed by surgery. About 40% to 45% of Wilms tumours are stage 1.

The tumour has grown into the renal pelvis (the hollow area in the centre of each kidney where urine collects), fat, soft tissue or blood vessels near the kidney. The tumour was completely removed by surgery. About 20% of Wilms tumours are stage 2.

The cancer has spread to nearby organs, blood vessels or lymph nodes in the abdomen. Cancer cells may have been spread before or during the surgery.

The tumour can’t be completely removed with surgery. About 20% to 25% of Wilms tumours are stage 3.

The cancer has spread outside of the abdomen to other parts of the body (called distant metastasis), such as to lymph nodes outside the abdomen, the lungs, the liver or bone. About 10% of Wilms tumours are stage 4.

A child with stage 4 Wilms tumour may still have a low local stage. For example, a child may have stage 1 Wilms tumour with a lung metastasis. The overall stage is stage 4 but with local stage 1 disease in the kidney.

The cancer is found in both kidneys. This is called bilateral Wilms tumour. About 5% of Wilms tumours are stage 5.

When a child has stage 5 Wilms tumour, each kidney is also given its own stage.

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.