If bone cancer is diagnosed, the doctor needs to know the stage, or extent, of the disease to plan the best treatment. Staging is a careful attempt to find out whether the disease has spread, and if so, to what parts of the body. The doctor may determine the stage of bone cancer at the time of diagnosis, or may need to give the patient more tests.
AJCC Staging System
One system used to stage all bone cancer is the American Joint Commission on Cancer (AJCC) system.
T stands for features of tumor size, N stands for spread to lymph nodes, M is for metastasis to distant organs, and G is for the grade of the tumor. This information about the tumor, lymph nodes, metastasis, and grade is combined in a process called stage grouping. The stage is then described in Roman numerals from I to IV (1-4).
T Stages of Bone Cancer:
N Stages of Bone Cancer
- TX: Primary tumor can't be measured
- T0: No evidence of the tumor
- T1: Tumor is 8 cm (around 3 inches) or less
- T2: Tumor is larger than 8 cm
- T3: Tumor is in more than one place on the same bone
M Stages of Bone Cancer
- N0: The cancer has not spread to the lymph nodes near the tumor
- N1: The cancer has spread to nearby lymph nodes
Grades of Bone Cancer
- M0: The cancer has not spread anywhere outside of the bone or nearby lymph nodes
- M1: Distant metastasis (the cancer has spread)
- M1a: The cancer has spread only to the lung
- M1b: The cancer has spread to other sites
TNM Stage Grouping
- G1-G2: Low grade
- G3-G4: High grade
After the T, N, and M stages 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. To determine the grouped stage of a cancer using the AJCC system, find the stage number below that contains the T, N, and M stages, and the proper grade.
All stage I tumors are low grade and have not yet spread outside of the bone.
- Stage IA: T1, N0, M0, G1-G2: The tumor is 8 cm or less.
- Stage IB: T2 or T3, N0, M0, G1-G2: The tumor is either larger than 8 cm or it is in more than one place on the same bone.
Stage II tumors have not spread outside the bone (like stage I) but are high grade.
- Stage IIA: T1, N0, M0, G3-G4: The tumor is 8 cm or less.
- Stage IIB: T2, N0, M0, G3-G4: The tumor is larger than 8 cm.
T3, N0, M0, G3-G4: Stage III tumors have not spread outside the bone but are in more than one place on the same bone. They are high grade.
Stage IV tumors have spread outside of the bone they started in. They can be any grade.
- Stage IVA: Any T, N0, M1a, G1-G4: The tumor has spread to the lung.
- Stage IVB: Any T, N1, any M, G1-G4 OR Any T, any N, M1b, G1-G4: The tumor has spread to nearby lymph nodes or to distant sites other than the lung (or both).
Even though the AJCC staging system is widely accepted and used for most cancers, bone cancer specialists tend to simplify the stages into localized and metastatic. Localized includes stages I, II, and III, while metastatic is the same as stage IV.
Knowing the stage assists the doctor in determining a prognosis. It also better helps you understand the care and treatment that will be required.