Osteosarcoma (adult)


Osteo means bone and sarcoma is a malignancy (cancer) of connective tissue, so Osteosarcoma (osteogenic sarcoma or OGS) is a cancer of bone cells. Although osteosarcoma is one of the more common bone tumors, it is rare type of cancer, with fewer than 1,000 new cases diagnosed each year in the United States.  

In adults, there is an increased incidence of osteosarcoma from 60 - 70 years but it can affect a person of any age.1   The most common sites for OGS are the bones around the knee (distal femur and proximal tibia) in the upper arm (humerus) or in the upper thigh (proximal femur).  But it can occur in any bone in the body including the spine, pelvis and skull.

Signs and Symptoms of Osteosarcoma

  • Pain – the pain experienced with an osteosarcoma is typically in the area of the tumor, which is often called local pain.
  • Swelling - there may be inflammation in the area of a tumor leading to swelling.
  • Decreased function – pain and swelling can contribute to a limited ability (or willingness) to use the affected extremity.
  • Fracture – the area of the bone where the tumor is located is weaker and more fragile than normal bone so fractures (called pathologic fracture) can occur in this area of the bone tumor.
  • Unintended weight loss – some people experience weight loss due to the body’s reaction to the cancer.
  • Night sweats – night sweats should be mentioned to a physician when accompanied by other symptoms listed 


Cause of Osteosarcoma

There is no evidence of a cause of bone cancer. There are situations that have been shown to increase the risk of developing bone cancer.  For instance, there is an association of OGS in adults who were diagnosed with Paget’s disease. This doesn’t mean that all individuals who have been diagnosed with Paget’s disease will develop osteosarcoma as adults but there has been an association identified. Other conditions that have been associated with osteosarcoma are:

  • Previous treatment using radiation therapy.
  • Hereditary conditions:
         Hereditary retinoblastoma
         Diamond-Blackfan anemia
         Li-Fraumeni syndrome
         Rothmund-Thomson syndrome
         Bloom syndrome
         Werner syndrome


Diagnostic Tests for Osteosarcoma

The first test that raises a suspicion for an osteosarcoma is an x-ray. When there is an osteosarcoma present the x-ray often shows an area with a ‘sun burst’ type pattern in the region where a person is experiencing the pain.  This pattern is caused by the cancerous bone-forming cells producing cancerous bone in a non-functional manner. Once a bone tumor is suspected it is very important that a patient sees an orthopedic oncologist before further testing or biopsy. Because it is a rare condition, bone cancer is best managed by a specialist who has training and experience in diagnosing and treating extremity sarcomas.

      MRI     An MRI enables the doctors to better see the full extent of the tumor. It is important to know if the tumor is ‘invading’ other tissues as treatment plans (such as surgical options) are being considered.
      Biopsy A biopsy is necessary to determine the exact type of tumor as well as its grade (aggressiveness). It is important that the biopsy be done by a specialist experienced in appropriate biopsy of extremity tumors. A biopsy done incorrectly may limit surgical options, and in some cases make amputation the only surgical option.
  Bone scan A bone scan is one of the tests done to help determine the extent of the cancer (staging). This is like an x-ray of your entire skeleton to see if there are any other areas of tumor.
  PET/CT scan This test is another that is necessary for staging of the cancer. It reveals if the cancer has metastasized to the abdomen, brain or other areas of the body


Osteosarcoma Grade and Staging

It is important to know how aggressive a tumor is (the grade of the tumor) as well as the stage of the cancer (has it spread to other area of the body). This information helps the physicians in determining the best approach to treatment, as well as assisting in discussions about prognosis.

Osteosarcoma Grade – when a pathologist looks at the tumor tissue under a microscope they can determine if the tumor has the tendency to grow quickly and spread. Osteosarcoma grades are:

    Low grade less likely to spread (metastasize)
    Intermediate grade moderately aggressive so may spread to other areas
  High grade more aggressive so likely to metastasize

Osteosarcoma Stage – stage combines the information from the diagnostic testing to determine the extent or severity of the disease process. The size of the tumor, if it has spread to other area such as the lungs, brain or other bones, as well as the grade are all considered when determining the stage. OGS staging is from I (one) to III (three) with stage I meaning the tumor is localized (only in the original site) and stage III indicating that the tumor has metastasized to other areas of the body.

Treatment of Osteosarcoma

Chemotherapy – “Chemo” is the use of medications to kill cancer cells and for treatment of osteosarcoma it is given systemically, meaning the medications enter the bloodstream and reach the cancer cells.

Depending on the treatment center, chemotherapy is given through the artery (intra-arterial) or through the vein (intravenous). Chemotherapy for OGS involves multiple courses of administration, for example the medications may be given once a week for several weeks.

Surgery – once the chemotherapy course is completed surgery is necessary to remove the bone tumor. It is very important that the entire tumor is removed in order to minimize the possibility that the tumor will return; therefore, the surgeon will remove a small amount of normal tissue around the tumor to better assure that no cancerous cells are left. Very careful surgical planning is necessary to accomplish complete removal (resection) of the bone tumor and maintenance of the patient’s best function.

Options can include:

  Resection Removal of the tumor without “rebuilding” the area that the tumor was removed from, more common in pelvic tumors than tumors in the extremity
  Resection with reconstruction Removal of the tumor and “rebuilding” with metal implants and/or bone allografts; soft tissue reconstruction may also be necessary
  Amputation Removing the extremity at a level above the tumor

Prognosis

Prognosis means ‘chance of recovery’ and is a question that is top of mind when any cancer diagnosis is received. There are factors that contribute to the prognosis of osteosarcoma.

Tumor site – the location of the tumor and whether there are tumors in more than one bone. Tumors in a location further from the center of the body have a better prognosis than those closer to the center of the body. Tumors in more than one bone indicate a later stage of the cancer which decreases the prognosis of survival.

Size of the tumor – larger tumors have a worse prognosis.

Presence of metastatic disease – the stage of cancer at the time of diagnosis contributes to prognosis. If disease has spread to the lungs or other sites the prognosis it is not as good.

Response to initial chemotherapy – when the tumor is resected during surgery it is tested to determine how much of the tumor died (indicating that the chemotherapy was effective). If the amount of necrosis (tissue death) is greater than 90% the prognosis is improved.

In general, the 5 year relative survival rate for adults diagnosed with bone cancer is ~ 70% 3. It is important to keep in mind that this rate includes people diagnosed with osteosarcoma at any stage. Prognosis does vary depending on stage at diagnosis.
 


References
1. American Cancer Society- Cancer Facts and Figures 2008 Exit Disclaimer. Atlanta, GA: American Cancer Society. Retrieved March 13, 2008

2. Malawer MM, Helman LJ, O'Sullivan B. Sarcomas of bone. In: DeVita VT, Hellman S, Rosenberg SA, editors. Cancer: Principles and Practice of Oncology. Vol. 2. 7th ed. Philadelphia: Lippincott Williams and Wilkins, 2007

3. National Cancer Institutes, SEER Program; http://seer.cancer.gov/csr/1975_2012