Staging is the process of finding out how far a cancer hasspread. The outlook (prognosis) for people with cancer depends, to a large extent, on the cancer's stage. The stage of a cancer is one of the most important factors in choosing treatment.

The stage of a Ewing tumor is based on results of imaging tests and biopsies of the main tumor and other tissues, which were described in the section "How are Ewing tumors diagnosed?"

AJCC staging system for bone cancer

A staging system is a standardized way in which the cancer care team describes the extent of the cancer. The American Joint Committee on Cancer (AJCC) has developed staging systems for most types of cancers. The AJCC uses one system to describe all bone cancers, including Ewing tumors that start in bone. Extraosseous Ewing (EOE) tumors (Ewing tumors that don't start in bones) are staged differently. They are staged like soft-tissue sarcomas. Information about soft-tissue sarcoma staging can be found in our document, Sarcoma - Adult Soft Tissue Cancer.

The AJCC staging system for bone cancers is based on 4 key pieces of information:

• T describes the size of the main (primary) tumor and whether it appears in different areas of the bone.

• N describes the extent of spread to nearby (regional) lymph nodes (small bean-shaped collections of immune system cells that are important in fighting infections). Bone tumors rarely spread to the lymph nodes.

• M indicates whether the cancer has metastasized (spread) to other organs of the body. (The most common sites of spread are to the lungs or other bones.)

• G stands for the grade of the tumor, which is a description of how the cells look under a microscope. Low-grade tumor cells look more like normal cells, and are less likely to grow and spread quickly, while high-grade tumor cells look more abnormal.

Numbers or letters appear after T, N, M, and G to provide more details about each of these factors.

T categories of bone cancer

N categories of bone cancer

M categories of bone cancer

Grades of bone cancer

(All Ewing tumors are considered to be G4.)

TNM stage grouping

Once the T, N, and M categories and the grade of the bone cancer have been determined, the information is combined and expressed as an overall stage. The process of assigning a stage number is called stage grouping. The stages are described in Roman numerals from I to IV (1-4), and are sometimes divided further.

Stage IA

T1, N0, M0, G1 to G2: The tumor is confined to the bone, is 8 cm across or less, and is low grade.

Stage IB

T2 or T3, N0, M0, G1 to G2: The tumor is confined to the bone, is either larger than 8 cm across (T2) or it is in more than one place on the same bone (T3). It is low grade.

Stage IIA

T1, N0, M0, G3 to G4: The tumor is confined to the bone, is 8 cm across or less, and is high grade.

Stage IIB

T2, N0, M0, G3 to G4: The tumor is confined to the bone, is larger than 8 cm across, and is high grade.

Stage III

T3, N0, M0, G3 or G4: The tumor is confined to the bone but has "skipped" to other sites in the same bone. (It is high grade.)

Stage IVA

Any T, N0, M1a, any G: The tumor has spread only to the lungs. (It can be any size or grade.)

Stage IVB (if either of these applies)

Any T, N1, any M, any G: The tumor has spread to lymph nodes. It can be any size or grade, and may or may not have spread to other distant sites.

Any T, any N, M1b, any G: The tumor has spread to distant sites other than the lung. It can be any size or grade.

Localized vs. metastatic stages

In practice, doctors rely on a simpler system for staging Ewing tumors to determine how best to treat them. In this system, the cancers are classified as either localized or metastatic.

Localized Ewing tumors

A localized Ewing tumor is thought to be confined to the area where it started and may also include nearby tissues such as muscle or tendons. A Ewing tumor is considered localized only after all of the imaging tests (x-rays, CT or MRI scans, and/or PET or bone scans) and the bone marrow biopsy and aspirate do not find distant spread to other organs.

Even when imaging tests do not show that the cancer has spread to distant areas, many patients are likely to have micrometastases (very small areas of cancer spread that can't be detected with tests), which is why chemotherapy is an important part of treatment for Ewing tumors.

Metastatic Ewing tumors

A metastatic Ewing tumor is one that has clearly spread from where it started to distant parts of the body. Most of the time, the spread is to the lungs or to other bones or the bone marrow. Less common sites of spread include the liver and lymph nodes.

About 1 in 4 patients will have obvious spread that is found by imaging tests. But as mentioned above, many other patients are likely to have small amounts of cancer spread to other parts of the body that can't be found by imaging tests.

Survival rates by stage

Survival rates are often used by doctors to produce a standard way of discussing a person's prognosis (outlook). The 5-year survival rate refers to the percentage of patients who live at least 5 years after their cancer is diagnosed. Of course, many people live much longer than 5 years. These numbers are based on people treated several years ago. Improvements in treatment since then will probably result in a more favorable outlook for patients now being diagnosed with Ewing tumors.

Survival statistics can sometimes be useful as a general guide, but they may not accurately represent any one person's prognosis. Other factors (such as those below) may also affect outlook. Your child's doctor is likely to be a good source as to whether these numbers may apply to your case, as he or she is familiar with the aspects of the particular situation.

Localized tumors

With modern treatment, the 5-year survival rate for patients with a localized Ewing tumor is around 70%.

Metastatic tumors

When metastases are present at diagnosis, the 5-year survival rate is about 20% to 30%. The survival rate is slightly better if the cancer has only spread to the lungs as opposed to having reached other organs.

Other factors affecting prognosis

Factors other than the stage of the cancer can also affect survival rates. Factors that have been linked with a better prognosis include:

• smaller tumor size
• main tumor located on an arm or leg (as opposed to pelvis)
• normal blood LDH level
• good tumor response to chemotherapy
• age younger than 10

Last Medical Review: 08/20/2009
Last Revised: 08/20/2009