Osteosarcoma or osteogenic sarcoma (also known as OS or osteo) is an aggressive malignant primary bone cancer. With about 600+ cases a year diagnosed in the United States, OS is the most prevalent bone cancer affecting children and adolescents/young adults.
Osteosarcoma can occur at any age but the most common age for diagnosis is in children and young adults during growth spurt times and often begins near the ends of leg or arm bones near joints. Osteosarcoma is rarer in other bones like the pelvis, shoulder, and jaw but unusual sites are increasingly seen in older adults. Given its rarity and time of usual diagnosis, it is common to be misdiagnosed as a benign tumor or dismissed as growing pains.
According to the American Cancer Society, most known risk factors for osteosarcoma are unavoidable. Other than radiation therapy, there are no known lifestyle-related or environmental causes of osteosarcoma, so there is no way to protect against this cancer. Known risk factors are:
Age: risk is highest between 10 and 30 especially during a growth spurt years which indicates it may be related to rapid bone growth
Height: usually tall for age which suggests it may be related to rapid bone growth
Gender and race/ethnicity: more common in males and in African Americans and Hispanic/Latino people
Paget disease of the bone: mostly affects people older than 50
Hereditary multiple osteochondromas: benign bone tumors
Inherited cancer syndromes:
• HereditaryRetinoblastoma:rare eye cancer which has a mutation in the RB1 gene
• Li-Fraumeni Syndrome: usually caused by abnormal changes in the TP53 gene
• Bloom syndrome, Werner syndrome and Diamond-Blackfan anemia, etc.
Osteosarcoma is diagnosed with a biopsy. Often osteosarcoma may be suspected from an x-ray or MRI but the only way to definitively diagnose osteosarcoma is for a pathologist to examine the tumor cells under a microscope.
A biopsy can be done in two different ways. The first method involves a small incision and a piece of tumor removed, this is called an open biopsy. The second method is called a needle biopsy where a needle is inserted into the tumor and a core of cells is removed for diagnosis.
Tests used to determine stage and plan for potential surgery:
After a diagnosis of osteosarcoma, additional testing is often done to determine the stage and prepare a treatment plan. Osteosarcoma is not staged by a traditional scale of 1-4 like many cancers. Instead osteosarcoma is usually staged as localized or metastatic. Localized osteosarcoma indicates that there is only one tumor in the primary site and no other evidence of disease elsewhere in the body. Metastatic indicates that there are two or more areas of disease in the body. Additional tests used to determine stage and treatment options include:
A bone scan is used to determine if there are other bones in the body with disease. This test involves an injection of a substance (nuclear tracer) into the vein that is taken up by bone that is actively growing. This nuclear tracer is detected by the medical equipment and creates an image of the patient’s skeletal structure that helps your doctor evaluate changes in bone metabolism. Bone metabolism is increased in areas of growth and in tumor(s).
A CT without contrast (or a CAT scan) will evaluate if there are any nodules in the lungs. This scan is performed to view thin slices (every 2-3 millimeters) of the lungs. Most protocols consider nodules 1 centimeter or larger to be concerning. Having a few very small nodules (2-3 mm) can be normal is people especially if they have recently had a cold. Usually contrast (a substance injected into the patient) is not used in CT scans of the lungs for osteosarcoma as the contrast is used to evaluate lymph nodes or other structures in the chest. This is usually not necessary information for osteosarcoma as lymph nodes are generally not impacted.
An MRI can be ordered with or without contrast to evaluate the primary tumor size and extension into the soft tissue/ muscle/ bone marrow (center of the bone). This test will show where the blood vessels and nerves are in relation to the tumor which will help with surgery planning.
A PET scan is typically not a standard scan for osteosarcoma, but your doctor may use it in conjunction with, or instead of a bone scan. This scan uses a sugar particle tagged with a tracer to evaluate tissue metabolism. Cancers often have increased metabolism so they tend to pick up a lot of the sugar.
An X-Ray allows the doctor to visualize the bone and tumor. The doctor can measure and determine the amount of destruction of the bone and if there are concerns for stability or fracture.
Tests used prior to chemotherapy:
Understanding how a patient’s body is functioning prior to chemotherapy is important to gauge any impact that chemotherapy could or does have upon treatment. Treatment is harsh on the body and doctors will always be considering the risks and benefits of treatment to the patient. Killing all the cancer cells with little or no future impact on the person’s body is important but each person and their bodies ability to handle these harsh treatments is different. So understanding a patient’s body before treatment and watching how their body is impacted by treatment is crucial.
An echocardiogram and EKG are done to test the functioning of the patient’s heart. Some of the chemotherapy agents can impact the function of heart muscle.
Blood tests are done to check for the functioning of bone marrow, kidneys and liver.
An audiogram is a test to assess hearing. One of the chemotherapies often used, cisplatin, can impact hearing.
Occasionally neurological functioning tests are done to determine if treatment has an impact on memory.
Generally treatment of osteosarcoma involves 10 weeks of chemotherapy followed by surgery to remove the tumor(s) and then a final 13 weeks of chemotherapy. Chemotherapy treatment can involve lots of needles and pokes. To minimize pokes and protect small veins from chemotherapy, a central line is often placed in a patient in a short surgical procedure. There are different types of central lines including; venous catheter (usually called a port) or Hickmann line. Your medical team will determine which is best for your situation.
Chemotherapy prior to surgery is called neoadjuvant chemotherapy. This is done to start killing the cancer cells as quickly as possible since choosing a surgical option and planning necessary to surgery can take longer than is optimal to begin treatment. The traditional chemotherapy regimen suggested for osteosarcoma by COG (Children’s Oncology Group in the United States) is called MAP. MAP consists of methotrexate, adriamycin (also called doxorubicin) and cisplatin (also called platinol).
Surgical options will differ depending upon the bone(s) impacted by the osteosarcoma, spread, ability to surgically get all the cancer out, future function requests and preference by the patient. For the long bones where traditionally osteosarcoma is found, arms and legs, surgical options often consist of limb salvage surgery or amputation (either traditional or rotationplasty for the leg). For lung nodules surgical options considered are thoracotomy or thoracoscopy. Rarer bone tumors in the pelvis, spine or jaw will often require a more unique approach to surgery and be specialized for the exact placement of the patient’s tumor.
Chemotherapy after surgery is called adjuvant therapy. This is done to continue killing any osteosarcoma cells that may be left in the body after surgery. Since the addition of adjuvant chemotherapy to osteosarcoma treatment, the relapse rates have decreased dramatically indicating the need for additional chemotherapy after surgery, even when the patient appears to be cancer free.