What are the stages of bone cancer?
After diagnosis, doctors will set about to determine the stage of bone cancer. Staging is the process of trying to find out the severity and spread of cancer. It further helps in understanding how serious it is and what treatment one must follow.
There are four cancer stages from I (1) through IV (4). By rule, the lower the number, the lower the spread of cancer. Although each patient has individual differences, approaches to a particular stage of cancer are by and large similar and usually receive similar treatment.
How do you determine the stage of cancer?
Doctors use diagnostic tests to determine the stage and metastasis of cancer. Knowing the stage helps them best predict the prognosis, treatment, and determining the chance for recovery.
The staging system the American Joint Committee on Cancer (AJCC) uses mostly is the TNM method. There are four primary pieces of information in this method:
1. The extent (size) of the tumor (T):
It indicates how extensive the cancer is and if it has affected more bones than one.
2. The spread of nearby lymph nodes (N):
It determines if cancer has spread to the lymph nodes.
3.The metastasis or the spread of cancer to the distant site (M):
It indicates if cancer has spread to either the lungs alone or distant sites such as the liver.
4.The grade of cancer (G):
It determines how abnormal the cells appear when viewed under a microscope. The grading scale for bone cancer is from 1 to 3. Low-grade (G1) cancers grow and spread slower than high-grade (G2 or G3) cancers.
Numbers or letters after initials T, N, and M help understand the factors that determine the stage of cancer.
Tumor:
The ‘T’ in the TNM system indicates the size and the location of cancer. Some stages have sub-stages as in the following:
Skeleton, trunk, skull, and facial bones have the following groups:
TX: the primary tumor cannot be evaluated
T0: there still is no evidence of the primary tumor
T1: the tumor is 8 cm or smaller
T2: the tumor is more significant than 8 cm
T3: there are more than one separate tumors in the primary site
Spine:
TX: the primary tumor cannot be evaluated
T0: There is no evidence of primary tumor
T1: the tumor is only found on one part of the vertebra, called the vertebral segment, or on two adjacent portions of the vertebrae
T2: the tumor is found only on three adjacent parts of the vertebrae
T3: the tumor is located on four or more nearing parts of the vertebrae, or in parts of the vertebrae that are not next to each other
T4: the tumor has grown into the spinal canal (T4a) or great vessels (T4b)
Pelvis:
TX: the primary tumor cannot be evaluated
T0: there is no evidence of primary tumor with no extraosseous extension
T1: the tumor is only in one part of the pelvis; where the tumor is 8 cm or smaller (T1a) or tumor is more significant than 8 cm (T1b)
T2: the tumor is found only on 1 part of the pelvis with extraosseous extension or on two parts of the pelvis with extraosseous extension; where the tumor is 8 cm or smaller (T2a) or tumor is larger than 8 cm (T2b)
T3: the tumor is found on two parts of the pelvis, with extraosseous extension; where the tumor is 8 cm or smaller (T3a), or tumor is more prominent than 8 cm (T3b)
T4: tumor is found on 3 parts of the pelvis or has crossed the sacroiliac joint, which connects the bottom of the spine with the pelvis; where the tumor involves the sacroiliac joint and has grown into the neural foramen (T4a) or the tumor has grown around blood vessels or affects blood flow (T4b)
Node:
The ‘N’ in the TNM system expands to lymph nodes. These are tiny; bean-shaped organs that help fight infection and help in immunity. The lymph nodes near the cancer are regional lymph nodes, while those away from the site are distant lymph nodes. The following are sub-stages of N grades:
NX: the regional lymph nodes cannot be evaluated
N0: cancer has not spread to regional lymph nodes
N1: cancer has spread to regional lymph nodes, and this is rare for primary bone cancer
Metastasis:
The ‘M’ in the TNM system indicates the spread of cancer to other body parts, that are distant.
M0: cancer is in early stages
M1: cancer has metastasized to other body parts; where when it has metastasized to the lungs it is M1a, or to other bones and organs it is M1b
Grade
Doctors also describe bone cancer by its grade (G), which indicates their health when viewed under a microscope. Doctors compare the cancer tissue to healthy tissue. The lower the tumor grade, the better the prognosis. The following are the sub-stages:
GX: tumor grade cannot be identified
G1: the cancer cells are well differentiated (low-grade)
G2: the cancer cells are moderately differentiated (high-grade)
G3: the cancer cells are poorly differentiated (high-grade)
The Number Stages
The tumor, node, and metastasis along with number stages.
In situ tumors are at stage 0. Detections in this early stage, show that it is small, low-grade and has not spread.
In stage 1A, the tumor is at low-grade not larger than 8 cm.
At stage 1B the tumor is longer than 8 cm. It is in more than one region of the bone.
Stage 2A is a high-grade tumor that is less than 8 cm across without having affected lymph nodes and without metastasis.
At stage 2B the tumor is a high-grade in more than one place in the same bone.
Stage 3 is a high-grade tumor in more than one place on the same bone.
In stage 4A, the tumor that has spread to the lung.
At stage 4B, the tumor has spread to the lymph nodes or other distant parts of the body.
