Bone Sarcoma and Subtypes

The second group of sarcoma is bone sarcomas or bone cancer. There are three types of bone sarcoma: osteosarcoma; Ewing’s sarcoma; and chondrosarcoma.  Bone sarcomas very rare with approximately 2,890 new cases diagnosed in the United States each year, and approximately 1,410 deaths. The incidence is slightly higher in males than females and no race has a higher incidence than another, although, Ewings sarcoma is  more among Americans of European descent. Bone sarcomas are very likely to be diagnosed in children; and due to the rarity and severity of bone cancer, a bone cancer specialist such as a pediatric oncologist or an orthopedic oncologist should be consulted in the treatment of the disease.

Bones consist of three types of tissue: compact tissue (the hard outer portion of the bone), cancellous tissue (spongy tissue inside the bone containing the bone marrow), and subchondral tissue (the smooth bone tissue of the joints). Cartilage surrounds the subchondral tissue to form a cushion around the joints.

Bone tumors can be benign (non-cancerous) or malignant (cancerous). Benign bone tumors are rarely life threatening and do not spread within the body; however, they can grow and compress healthy bone tissue. Cancer that develops in the bone is called primary bone cancer. It is differentiated by secondary bone cancer which spreads to the bone from another part of the body. Primary bone cancer is rare with approximately 2,500 new cases diagnosed each year in the United States (this figure includes bone cancer which is not sarcoma).

The most common type of primary bone cancer is osteosarcoma. Because it occurs in growing bones, it is most often found in children. Another type of primary bone cancer is chondrosarcoma which is found in the cartilage. This cancer occurs more often in adults. Ewing’s sarcoma can occur as either a bone sarcoma or a soft tissue sarcoma depending upon the original location in the tumor.

Scientists are uncertain what causes bone cancer however they have been able to identify some factors which may put a person at risk. Children and young adults who have had undergone radiation therapy or chemotherapy for other diseases are at increased risk for bone cancer. Additionally, adults with Paget’s disease which is a disease characterized by abnormal growth of new bone cells have an increased risk of osteosarcoma. There are also some hereditary conditions which can increase the risk of bone cancer.

Symptoms of bone cancer can vary depending on the size and location of the tumor. Pain is the most common symptom. Tumors arising in or around the joints often cause swelling and tenderness. Tumors can also weaken the bones thus causing fractures. Some other symptoms can be weight loss, fatigue and or anemia.

The first step in diagnosing primary bone cancer is a complete medical history and physical examination performed by a physician. The doctor may order a blood test to determine the level of an enzyme called alkaline phosphatase. Approximately 55% of patients with primary bone cancer will have elevated levels of alkaline phosphatase. However, it isn’t a completely reliable indicator for bone cancer since growing bones in children will cause the enzyme to be elevated.

X-rays are also used to locate a tumor. If an x-ray suggests a tumor is present than a doctor may require further testing such as a CT scan, Magnetic Resonance Imaging (MRI), or an angiogram. Finally, a biopsy must be performed to determine if cancer is present. A biopsy is a procedure used to remove sample tissue from the tumor. A surgeon, usually an orthopedic oncologist, performs the procedure using a needle or making an incision. During a needle biopsy the surgeon makes a small hole in the bone and removes sample tissue with a small instrument. During an incisional biopsy, the surgeon cuts into the tumor and removes sample tissue. A Pathologist (a doctor specializing in identifying disease) then studies the cells and tissues under a microscope to determine whether the tumor is cancerous.

The treatment of bone cancer depends on the size, location, type and stage of the cancer. Chemotherapy with surgery is often the primary treatment. While amputation of a limb is sometimes necessary, using chemotherapy either before or after surgery has allowed physicians to save the limb and improve survival in many cases. Radiation may be used in Ewing’s sarcoma is surgery is not feasible or in certain select cases of metastatic disease.

New and more effective treatments are being developed in clinical trials at many hospitals and cancer centers in the United States.

Ewing’s Sarcoma

Ewing’s sarcoma is actually several types of sarcomas known as the Ewings Family of Tumors. In the U.S., there are approximately 250 cases diagnosed a year, generally in children and young adults under the age of 30.  It can be found in any bone, but is most common in the bones of the lower body such as the pelvis, tibia (shin), fibula (shin), and femur (thigh).  Ewing’s sarcoma is often associated with a chromosomal translocation between genes EWS and FLI1 on chromosomes 22 and 11.  Although Ewings is classified as a bone cancer, the type of cells it originates in is not completely known, which is why as mentioned above, occasionally Ewing’s sarcoma may occur in soft tissues,  Peripheral Primitive Neuroectodermal Tumor (peripheral PNET) is a rare tumor that has the same translocation, and is now considered to be identical to Ewings.  The Ewings Family of Tumors (EFT) includes Ewing’s sarcoma of bone, extraosseous Ewings, and peripheral PNET. It is not known what causes the tumor, although it is more likely to occur in people of European descent.  It is an aggressive cancer and is treated with a combination of surgery, radiation, and chemotherapy, with a good outcome for many cases.

 

Chondrosarcoma

Chondrosarcoma is a cancer that develops from the cells that produce cartilage.  A little less than one-third of bone sarcomas are chondrosarcomas. While the disease can affect people of any age, unlike most other forms of skeletal system cancer, it is more common among older people than among children. Also unlike the other bone cancers chondrosarcoma is more often found in the spine and pelvis than in legs or arms.  Surgery is the most common treatment for chondrosarcoma, sometimes with radiation or chemotherapy as well.

Osteosarcoma (Osteogenic Sarcoma)
Osteosarcoma is a malignant (cancerous) bone tumor that occurs predominantly in adolescents and young adults. It accounts for approximately 5% of the tumors in childhood. the bones most frequently involved are the large bones of the upper arm (humerus) and the leg (femur and tibia). In children and adolescents, 80% of these tumors arise from the bones around the knee. It is slightly more common in males than females. It is the most common primary malignant bone tumor with the exception of myeloma. Although osteosarcoma is a common malignant bone tumor, it is still rare with less than 1,000 new cases each year in the United States. Due to its rarity, it is imperative that patients with proven or suspected osteosarcoma have an initial evaluation by an orthopedic oncologist familiar with the management of this disease. This evaluation should be done prior to the initial biopsy, since an inappropriately performed biopsy may jeopardize a limb-sparing procedure.

Osteosarcoma occurs in adolescents at the time they are most rapidly growing in their most rapidly growing bones; therefore, it is suspected that rapid bone growth may play a role in the development of osteosarcoma. Additionally, some evidence suggests that chronic bone injury can increase the risk for osteosarcoma. When osteosarcoma occurs in adults over age 40 it is usually associated with a pre-existing condition such as Paget’s disease.

The initial symptoms include pain, often in and around the knee, especially in tumors on the tibia or femur. The pain typically worsens over time and is not related to the time of day. Swelling and tenderness typically occur late in the course of osteogenic sarcoma, followed by a large soft tissue mass appearing. A screening of serum alkaline phosphatase levels may be done. These levels are high in approximately 45-50% of patients with osteosarcoma; therefore it cannot be used alone to diagnose the disease.

Osteosarcoma must be diagnosed by biopsy. Because the disease commonly spreads (metastasizes) to other parts of the body, especially the lungs, chest x-rays, lung tomograms, CT scans of the chest , and an x-ray skeletal survey or bone scan may be done before treatment. This process is called staging. There are three groups used to describe the extent of the disease: Localized – the cancer cells have not spread beyond the bone or nearby tissue. Metastatic – the cancer cells have spread from the bone where the cancer began to other parts of the body (commonly the lungs, however it can spread to other bone). Recurrent – the cancer has come back after it has been treated. It may come back to the original site of the tumor or another part of the body.

Surgery is the primary method of treatment. This can be either an amputation or limb-sparing procedure. A limb-sparing procedure is when a surgeon removes the tumor and a block of surrounding tissues to ensure clean (cancer free) margins around the tumor. The surgeon then reconstructs the limb using prosthetic devices, bone grafts or other reconstructive techniques. These procedures are highly specialized and are usually performed by an orthopedic oncologist. In general 70-90% of osteosarcomas of the limb can be treated by a limb-sparing procedure and do not require amputation; therefore, before undergoing an amputation, it is recommended that the patient seek the advice of an orthopedic oncologist.

Surgery is usually followed by a course of chemotherapy using one or more anti-cancer drugs. Some clinical trials have shown that adjuvant chemotherapy ( chemotherapy given when no clear evidence of cancer can be found i.e. after the tumor is removed) may be helpful in preventing the relapse or recurrence of the disease. Other trials suggest that there is no difference in outcome between pre-operative chemotherapy or adjuvant chemotherapy.

Parosteal osteosarcoma
Parosteal osteosarcoma is a low grade tumor that arises on the surface of the bone. It rarely penetrates the center of the bone and rarely becomes a highly malignant osteosarcoma. It accounts for approximately 4% of all osteosarcomas and is slightly more common in females than males. It is different than classic osteosarcoma in that it typically arises in adults between the ages of 20 and 40. It has a better prognosis than classic osteosarcoma with an overall survival rate of 75% to 85%. It has a very slow rate of metastases (spreading).

Parosteal osteosarcoma is most commonly found on the femur, behind the knee (72% of all cases). It usually presents itself with minimal pain and tenderness and in its typical location behind the knee there may be some restriction in movement of the knee joint.

Surgery with wide margins is the standard treatment for parosteal osteosarcoma, either by amputation or limb-sparing surgery. Because they are located at the end of the bone, are typically low grade, and lack local invasiveness, they are often amenable to limb-sparing procedures. Grade III parosteal lesions usually require chemotherapy because of the risk of metastases.

Periosteal osteosarcoma
Like parosteal osteosarcoma, periosteal osteosarcoma is an uncommon tumor arising on the surface of the bone, most commonly the tibia. It is a high grade tumor composed of malignant cartilage. It occurs in a younger age group and is even more common among females than males than parosteal osteosarcoma. Because periosteal osteosarcoma is more likely to metastasize than the parosteal, some oncologists treat this tumor more aggressively with combination therapy such as surgery and chemotherapy.

Multifocal Sclerosing osteosarcoma
Multifocal sclerosing osteosarcoma is an extremely rare form of osteosarcoma. It tends to occur in children less than 10 years old and represents less than 3% of all primary osteosarcomas. It is an aggressive tumor which presents as a single painful tumor, much like other types of osteosarcoma. However further tests looking for metastases reveal tumor in virtually all of the skeleton.

Since all the bones of the body are involved surgery is usually not an option, except to relieve pain. Aggressive chemotherapy can lead to a remission; however, multiple tumors eventually progress and mortality approaches 100%.

Osteosarcoma of the Jaw and Skull
Osteosarcoma of the craniofacial bones are relatively rare and represent less than 10% of all osteosarcomas. They typically occur in patients between the ages of 20 and 40 and have the same occurrence rate between males and females. The bones most commonly affected are the mandible (jaw bone) and the maxilla (cheek bone). Because they are located in the head and neck, they tend to be diagnosed earlier and can remain localized for longer periods of time; however, they are more difficult to remove surgically and therefore local recurrence is common.

Treatment of malignant osteosarcoma in the skull bones is similar of classic osteosarcoma. It should include preoperative chemotherapy. This is extremely important due to the limited margins available for surgical excision.

Osteosarcoma in Paget’s Disease
Paget’s disease affects approximately 3% of the population over the age of 60. It is characterized by abnormal growth of new bone cells leading to multiple bone deformities. Approximately 1% of patients with Paget’s disease develop primary bone sarcoma. The tumors usually arise in the pelvis, femur, or humerus. They typically are large and very destructive making surgery difficult. At the time of diagnosis, the cancer has often metastasized to the lungs. Amputation is sometimes necessary.

Patients with suspected osteosarcoma arising in Paget’s disease should receive a bone scan and x-ray of all identified tumors. Additionally, a CT scan of the chest should be done to rule out metastases to the lungs. Treatment is the same as fully malignant osteosarcoma arising in a younger population. Patients with preoperative chemotherapy, radical surgery of the tumor, followed by post-operative chemotherapy have the best prognosis. Tumors arising in the skull and spine are sometimes inoperable. In this instance patients are typically given chemotherapy and radiation therapy to control and shrink the tumor. Great care must be taken during chemotherapy treatments since many older patients have impaired kidney function.

Post-irradiation Osteosarcoma (Radiation Induced)
Radiation Induced Osteosarcoma is a rare form of osteosarcoma which occurs in people who have undergone radiation therapy treatments for other diseases. The average length of time before these tumors appear is 10 years following radiation. The younger the patient is at the time of radiation, the higher the risk of osteosarcoma. Additionally, evidence suggest that patients who receive higher doses of radiation are at a higher risk of developing osteosarcoma than patients who receive lower doses of radiation.

Post-irradiation osteosarcomas are most commonly located in the spine, pelvis, hips and shoulders. People with retinoblastoma, a malignant tumor of the eye, are at a higher risk of developing post-irradiation osteosarcoma due to a defect in the RB gene.

Symptoms of postirradiation osteosarcoma are painful swelling in and around the area of radiation. A biopsy must be performed in order to diagnose the disease. Once the diagnosis is made, staging of the tumor is done using bone scan, CT scan or MRI. Additionally a CT scan of the lungs should be done to rule out metastases to the lungs.

The treatment of postirradaition sarcoma is similar to classic osteosarcoma. It usually included preoperative chemotherapy, surgery and followed by postoperative chemotherapy. Surgery can be difficult when tumors are in and around the spine and therefore preoperative chemotherapy to shrink the tumor is crucial. Due to this challenge, the prognosis for postirradiation osteosarcoma is worse than that for classic osteosarcoma.