Osteosarcoma: Staging and Treatment
What is staging for cancer?
Staging is the process of learning how much cancer is in your body and where it is. Tests like bone X-Ray, bone scan, biopsy, CT, MRI, and PET scan may be done to help stage your cancer. Your providers need to know about your cancer and overall health so that they can plan the best treatment for you.
Staging looks at the size of the tumor and where it is, and if it has spread to other organs. There are two systems used to stage osteosarcoma:
1. The Musculoskeletal Tumor Society (MSTS) staging system, also called the Enneking system. It has three parts:
- G- Describes the grade of the tumor. Grade is based on what the cancer looks like under a microscope. It can be either “low grade” (G1) or “high grade” (G2). Low-grade tumors look more like normal cells and high-grade tumors look more abnormal.
- T- Describes the extent of the “primary” tumor. The tumor can be kept to the bone, called “intracompartmental (T1)” or the tumor can spread beyond the bone to nearby tissue or organs, called “extracompartmental (T2).”
- M- Describes if the cancer has spread to other organs (called metastases). Tumors that have not spread are considered M0, while tumors that have spread are M1.
2. The “TNM system,” as described by the American Joint Committee on Cancer. It has three parts:
- T- Describes the size/location/extent of the "primary" tumor in the bone.
- N- Describes if the cancer has spread to the lymph nodes.
- M-describes if the cancer has spread to other organs (called metastases).
How is osteosarcoma staged?
Staging for osteosarcoma is based on:
- The size of your tumor on imaging tests and what is found after surgery.
- If there is spread to other organs (metastasis).
- If there is cancer in your lymph nodes.
The staging systems can be very complex. Below is a summary. Talk to your provider about which system is used and the stage of your cancer.
Musculoskeletal Tumor Society (MSTS) System
Stage IA (G1, T1, M0): The tumor is low grade (G1), intracompartmental (T1), and has not spread to the lymph nodes or other organs (M0).
Stage IB (G1, T2, M0): The tumor is low grade (G1), extracompartmental (T2), and has not spread to the lymph nodes or other organs (M0).
Stage IIA (G2, T1, M0): The tumor is high grade (G2), intracompartmental (T1), and has not spread to the lymph nodes or other organs (M0).
Stage IIB (G2, T2, M0): The tumor is high grade (G2), extracompartmental (T2), and has not spread to the lymph nodes or other organs (M0).
Stage III (G1 or G2, T1 or T2, M1): The tumor is low grade (G1) or high grade (G2), intracompartmental (T1) or extracompartmental (T2), and has spread to lymph nodes or other organs (M1).
The TNM System
The TNM system below is used mostly for osteosarcoma tumors of the arms, legs, trunk, skull, or facial bones. It is not often used for cancer that starts in the pelvis or spine. If you have cancer that started in the pelvis or spine, talk with your provider about how your cancer is staged.
Stage IA (T1, N0, M0, G1 or GX): The main tumor is no more than 8 centimeters (cm), or about 3 inches wide. The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0). The cancer is low grade (G1), or the grade cannot be determined (GX).
Stage IB (T2-T3, N0, M0, G1 or GX): The main tumor is more than 8 cm wide (T2) or there is more than one tumor in the same bone (T3). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0). The cancer is low grade (G1), or the grade cannot be determined (GX).
Stage IIA (T1, N0, M0, G2 or G3): The main tumor is no more than 8 cm wide (T1). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0). The cancer is high grade (G2 or G3).
Stage IIB (T2, N0, M0, G2 or G3): The main tumor is more than 8 cm wide (T2). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0). The cancer is high grade (G2 or G3).
Stage III (T3, N0, M0, G2 or G3): There is more than one tumor in the same bone (T3). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0). The cancer is high grade (G2 or G3).
Stage IVA (Any T, N0, M1a, Any G): The main tumor can be any size, and there may be more than one in the bone (Any T). The cancer has not spread to nearby lymph nodes (N0). It has spread only to the lungs (M1a). The cancer can be any grade (Any G).
Stage IVB (Any T, N1 or Any N, Any M or M1b, Any G): The main tumor can be any size, and there may be more than one in the bone (Any T). The cancer has spread to nearby lymph nodes (N1) or might not have spread to nearby lymph nodes (Any N). It may or may not have spread to distant organs like the lungs or other bones (Any M) or it has spread to distant parts of the body, such as other bones, the liver, or the brain (M1b). The cancer can be any grade (Any G).
How is osteosarcoma treated?
Treatment for osteosarcoma depends on many things, like your cancer stage, age, overall health, and testing results. Your treatment may include some or all of the following:
Surgery
You will need to go to an orthopedic surgeon (a doctor who specializes in surgery on bones and joints) who has experience with osteosarcoma tumors. Whenever possible, a biopsy and surgery to remove the tumor should be planned together. The goal of surgery is to remove all of the cancer. The tumor plus some normal tissue around the tumor are removed to lessen the chance of the cancer coming back after surgery.
Two main types of surgery for osteosarcoma in the limbs are:
- Limb-salvage surgery: Also called limb-sparing. The tumor must be in the arm or leg. The surgeon tries to remove all of the tumor while saving the nearby ligaments, tendons, nerves, and blood vessels so that you can still use your limb as before. If the tumor cannot be removed without affecting the rest of the limb, amputation may be needed.
- Amputation: If your tumor is very big or if it reaches into blood vessels or nerves, the limb may need to be removed. Your surgeon will look at MRI scans to plan how much of the limb should be removed. Most times, your surgeon will round off where the amputation is made so that it will fit into a prosthetic (artificial) limb.
Surgery for tumors in other parts of the body may include:
- Pelvic (hip): It can be hard to remove the whole tumor with surgery. Often, chemotherapy is given before surgery to try to shrink the tumor. Radiation therapy may also be given after surgery to get rid of all of the cancer.
- Lower jawbone: The whole lower part of the jaw may be removed. The jaw can later be replaced with bones from other parts of the body. Radiation therapy may also be used if the whole tumor can’t be removed.
- Spine or skull: Most often need a combination of chemotherapy, radiation, and surgery to treat tumors in these bones.
- Joint fusion: Also called “arthrodesis.” Some tumors in joints are hard to remove while keeping the joint in working order. Surgery can be done to fuse the two bones of the joint together.
The most important part of surgery for osteosarcoma is the physical therapy and rehabilitation that happens after surgery. Your care team will help set you up with physical, occupational, and other therapies. These will help you cope with changes to function and mobility.
Chemotherapy
Most osteosarcoma tumors are treated with chemotherapy for up to 10 weeks before surgery and for up to 1 year after surgery. Two or more drugs are often given together. Some medications used to treat osteosarcoma are:
Targeted therapies including regorafenib, sorafenib, cabozantinib, and everolimus may also be used in the treatment of osteosarcoma.
Radiation Therapy
Radiation therapy uses high-energy rays kill cancer cells. Radiation therapy has a hard time killing osteosarcoma cells, so it is often used in combination with surgery and/or chemotherapy. Surgery may be done to remove as much of the tumor as possible and then radiation is given to try to kill of any leftover cancer cells. The most common type of radiation used for osteosarcoma is external beam radiation therapy. Another type of radiation therapy used for bone tumors uses radioactive medications, like samarium-153-EDTMP and radium-233. These medications are injected into a vein and they collect in the bones. Once they are in the bones, they start to kill off cancer cells with their radiation.
Clinical Trials
You may be offered a clinical trial as part of your treatment plan. To find out more about current clinical trials, visit the OncoLink Clinical Trials Matching Services.
Making Treatment Decisions
Your care team will make sure you are included in choosing your treatment plan. This can be overwhelming as you may be given a few options to choose from. It feels like an emergency, but you can take a few weeks to meet with different providers and think about your options and what is best for you. This is a personal decision. Friends and family can help you talk through the options and the pros and cons of each, but they cannot make the decision for you. You need to be comfortable with your decision – this will help you move on to the next steps. If you ever have any questions or concerns, be sure to call your team.
You can learn more about bone cancer at OncoLink.org.