Bone Cancer Stages
The staging process for all bone cancer uses the American Joint Commission on Cancer (AJCC) system. This process can be divided into two phases: the evaluation of the cancer’s specific traits and an overall outlook based on the grouping of that evaluation’s findings. The groupings are labeled by Roman numerals I through IV, according to the severity of the cancer.
Bone cancer is uncommon and can begin in any bone. It most often occurs in longer bones, such as those in the legs and arms. The term “bone cancer” does not apply to any cancer that begins outside of the bones or in bone marrow blood cells. Cancer that has spread to the bone from elsewhere is named for the point of origin.
The AJCC system is used to stage bone cancer. Within this system, several traits of the cancer are determined and then combined to provide an overall outlook, known as “stage grouping.” The traits are labeled by four different stages, according to the size of the tumor (T), the spread of the cancer to lymph nodes (N), the spread-or metastasis-of the cancer to other organs (M) and the grade of the tumor (G).
After these characteristics have been evaluated, they are grouped together to provide a stage number. The stage groupings are labeled I, II, III and IV.
The T stages of bone cancer include a tumor that cannot be measured (TX), no evidence of a tumor (T0), a tumor of eight centimeters or less (T1), a tumor larger than eight centimeters (T2) and a tumor in more than one place on one bone (T3). The N stages consist of a cancer that has not spread to the lymph nodes around the tumor (N0) or a cancer that has (N1).
The M stages are listed as cancer that has not metastasized to the lymph nodes or outside of the bone (M0) or one that has metastasized (M1). The M1 stage is also grouped into two subcategories: M1a means the cancer has spread to the lung and M1b means it has spread to other sites.
Bone Cancer Grading
Bone cancer grading is simply broken into two categories, according to how aggressive the cancer is. G1 or G2 signifies a low-grade (less aggressive) cancer, while G3 or G4 signifies a high-grade (more aggressive) cancer.
Stage Grouping (Overall Stages)
The T, N, M and G stages are combined to determine the extent of the cancer. It then fits into one of the following stage groupings, summarized by the Mayo Clinic:
- Stage I bone cancer has not spread outside of the bone and would not be considered aggressive.
- Stage II bone cancer is also limited to the bone, but it would be considered aggressive.
- Stage III bone cancer is occurring in multiple places within the same bone.
- Stage IV bone cancer has spread to places outside of the bone.