Osteosarcoma (also called osteogenic sarcoma) is a type of cancer that starts in the bones. It is the most common type of bone cancer. It is a very aggressive malignant tumor. Definition of osteosarcoma is understood when the word is divided into two parts: osteo and sarcoma. Osteo is the part related to bones. Sarcoma is the kind of tumor that arises from bone, cartilage, fat, muscle, vascular, or hematopoietic tissue. They are the opposite of “carcinomas” which are tumors arising from abnormal epithelial tissue.
What is Osteosarcoma?
Osteosarcoma is most common in children and teenagers, but it can occur in any age. It comprises 2.4% of all malignancies in pediatrics, and about 20% of all primary bone cancers. The reason that it is common in children and young adults is because it usually develops in areas where the bone is growing quickly such as near the end of long bones with 42% growing in the distal femur (the lower part of the thigh bone), 19% in the proximal tibia (the upper part of the shinbone) and 10% growing in the proximal humerus (the part of the upper arm bone close to the shoulder). However osteosarcoma can also develop in any part of the body including the bones of the hip, the jaw and the shoulder, which comprises 8% of the total osteosarcoma incidence. This is especially common in adults.
Osteosarcoma is the most common type of bone cancer, and the sixth most common type of cancer in children. The second most common type of bone cancer in children is Ewing’s sarcoma. This type of sarcoma is characterized by developing also in the long bones as well as the vertebrae (the spinal cord).
How cancer works:
To understand osteosarcoma we have to understand what happens in the body when it has cancer. Cancer occurs due to uncontrollable division or growth of abnormal cells in the body (called metaplasia or dysplasia). In most cases these abnormal cells don’t progress to tumors, they undergo apoptosis (programmed cell death) but in the case of cancer, they keep growing until they invade other “healthy” tissues. This is a process called metastasis. When the abnormal cells develop into the metastasis stage, the cancer has already moved into the bloodstream or the lymph vessels.
Cancer is caused when the cell DNA mutates to activate oncogenes (genes that stimulate cell growth) and deactivate tumor suppressor cells. Osteosarcomas are either localized or metastatic.
Osteosarcoma prognosis can be divided into three stages:
- Stage I: It includes low grade, localized tumors such as parosteal osteosarcoma and intramedullary or intraosseous, well-differentiated osteosarcoma. Parosteal osteosarcoma rises to the surface of the bone instead of deep inside it. It is usually found around the knee. Stage I is characterized by being very slow growing. The tumors look like normal bone and have few dividing cells. The tumor is 8 cm or less and has not spread to nearby lymph nodes. Survival prognosis is very high (>90%).
- Stage II: These are intermediate and sometimes high grade tumors such as periosteal osteosarcomas. This stage is a very rare type. The tumor has not spread to nearby lymph nodes. Survival prognosis is 20%-50% according to the degree of metastasis.
- Stage III: These are the fastest growing type osteosarcomas. They are high grade, metastatic tumors. The tumors deviate from normal bone cells and have many cells in the division process. These are most common in children and teenagers. The tumor has spread to the lungs or the lymph nodes or both. Overall survival prognosis doesn’t exceed 30%.
Types of Stage III osteosarcoma include:
- Chondroblastic: The tumor invades cartilage tissue as well as bones.Fibroblastic: Only a small amount of bone is made by the tumor cells.
- Small cell: Tumor cells are seen under the microscope as small, round cells.
- Telangiectatic: The tumor forms abnormal blood vessels as well as bones.
Survival rate for osteosarcoma depends on the condition of the tumor itself. In case of localized osteosarcoma, the 5-year survival rate is 60%-80%. The 5-year survival rate is the percentage of patients who have lived at least 5 years after their diagnosis. In case of metastatic tumors, the 5-year survival rate is 15%-30%. It can go up to 40% if the cancer has only spread to the lungs or if all the tumors could be removed surgically.
Osteosarcoma signs and symptoms:
The signs and symptoms of osteosarcoma are usually three definitive manifestations: pain, swelling and fracture.
Pain in the affected bone is variable and it intensifies at night. It increases with activity and is usually accompanied by formation of a lump or a mass. Teenagers who practice sports usually complain of pain in their lower femur, accompanied by slight swelling according to the size of the tumor.
Swelling of the limb as a whole or the affected area specifically is the second common symptom of osteosarcoma. Unfortunately the swelling will sometimes be manifested as a casual bruise that doesn’t go away, so this might delay the diagnosis. If the swelling is in a place not too visible, such as the pelvis, it might also go unnoticed.
Bone fractures occur due to the change in the bone cell structure. It becomes weaker than normal bones and is described by osteosarcoma patients as one that has gone sore for weeks before it suddenly became very painful. This symptom is most common in stage III osteosarcomas such as the Telangiectatic.
Osteosarcoma diagnostic methods:
Osteosarcoma is diagnosed mainly through an X-ray followed by a series of scans (CT scan, PET scan, bone scan, MRI). The last step is a biopsy which could be done in either of two ways:
- Needle Biopsy: It could be done either with a large, hollow needle (Core Needle Biopsy) to remove a small cylinder of the tumor tissue, or with a very thin needle attached to a syringe (Fine Needle Aspiration Biopsy) to withdraw some of the cells and fluid from the tumor tissue. If the tumor is too deep, the doctor will guide the needle into the tumor while viewing a CT scan.
- Surgical Biopsy: The surgeon cuts a piece of the tumor with the patient under general anesthesia.
The biopsy of suspected osteosarcoma must be done with great care and precision by a qualified orthopedic oncologist. The biopsy is the only method by which the nature of the tumor is determined, whether malignant or benign.
Osteosarcoma: Causes and Underlying factors:
Until now the main cause of osteosarcoma is unknown. Researchers have found that the most underlying cause of osteosarcoma is related to underlying conditions. In a study conducted in 1990, it was found that the higher percentage of fluoride there was in drinking water, the greater chance it was for developing osteosarcoma. In 2001, a PhD dissertation written by a professor at the Harvard School of Dental Medicine indicates a strong link between exposure to fluoride between the ages of 6-8 and the development of osteosarcoma in young boys. It is notable that this age group represents the mid-childhood growth spurt during which bones are observedly elongated.
Inheritance plays a huge role in predisposition for osteosarcoma. Some people have rare, inherited cancer genes or syndromes and thus are more likely to develop osteosarcoma. Among these cases are:
- Hereditary retinoblastoma.
- Rothmund–Thomson syndrome.
- Li-Fraumeni syndrome.
- Bloom syndrome.
- Werner syndrome.
- Diamond-Blackfan anemia.
Certain bone diseases play a huge factor in predisposing for osteosarcoma including:
- Paget’s disease of bone.
- Hereditary multiple osteochondromas, which are usually benign bone tumors formed by bone and cartilage. In rare cases they develop into the more malignant sarcoma.
Risk factors that might predispose for osteosarcoma include rapid bone growth, the African American ethnicity and radiation therapy. It occurs in males more than females.
How is Osteosarcoma treated?
According to the American Cancer Society, treatment options for osteosarcoma are through surgery, chemotherapy or both. In some rare cases, radiation therapy is favored.
For surgery, an orthopedic oncologist might consider various options depending on whether the tumor is metastatic or localized. It also depends on the location of the sarcoma.
For tumors in the arms or legs, treatment options are either limb-salvage therapy or the more drastic action of amputation.
Limb-sparing (limb-salvage) therapy is a very complex operation. It depends on the size of the tumor and its location. It also relies a great deal on the skill of the orthopedic surgeon because great care should be applied when removing the tumor such that most of the tendons, blood vessels, muscles and nerves of the limb are spared. This is required to keep it as healthy as possible. The section of bone removed along with the tumor is replaced with a bone graft or with an internal prosthesis.
For patients who undergo amputation, a surgeon decides exactly how much of the limb needs to be amputated. The remaining muscle and skin is arranged as a cuff around the remaining bone so that the prosthetic limb would fit into it.
For pelvic tumors, a combination of chemotherapy and surgery is required. Sometimes radiation therapy is also a step in the treatment process.
A tumor in the lower jaw bone may require complete removal of the lower half of the jaw and later replaced with bones from other parts of the body. Radiation therapy is usually a follow up treatment option.
Osteosarcomas in the spine or skull always require the combination therapy of chemotherapy and surgery, followed by radiation.
In metastatic tumors, osteosarcomas usually spread to the lungs. Surgery might not be always a valid option in that case. It depends on the size of the tumors and the number of tumors that have traveled to the lungs. Sometimes surgery couldn’t be done because tumors are present next to vital structures in the lungs such as large blood vessels. In case of renal failure patients, heart disease patients and acute liver failure patients, surgery wouldn’t be the right option to remove the metastases because the patient won’t be able to withstand anesthesia and the grave surgical procedures.
Most osteosarcomas are treated with neoadjuvant chemotherapy for 10 weeks, followed by surgery and finally adjuvant chemotherapy for up to a year.
The drugs used often to treat osteosarcoma include:
- Methotrexate (given with leucovorin to help prevent its side effects)
- Cisplatin/ carboplatin
Two or more of these drugs are given as combination therapy either to minimize side effects or to increase efficacy.
Apart from humans, osteosarcoma is the most common bone cancer found in dogs. It typically affects middle-aged, giant breed dogs such as:
- Irish Wolfhounds.
- German Shepherd.
- Great Pyrenees.
- Bernard (hereditary causes).
- Doberman Pinschers.
- Great Danes.
Canine osteosarcoma is very aggressive in dogs, far more than humans. The long term prognosis is very poor and treatment is usually ineffective.
Signs and symptoms of canine osteosarcoma include swelling of the joint or affected bone, tenderness and pain. Dogs that develop it are described by their owners as “tired in appearance and anorexic”. Eventually a lump or a painful inflammation is observed on the affected site.
Osteosarcoma is more common in dogs that have suffered a blunt bone injury. Neutered dogs are two times more liable to osteosarcoma than their intact peers.
The most commonly affected bones in dogs are the proximal humerus, the distal radius, the distal femur, and the tibia followed closely by the ribs, the mandible, the spine, and the pelvis. Metastasis is either to the lungs or the surrounding lymph nodes.
Treatment usually includes amputation. Even with neoadjuvant chemotherapy combined with surgery, dogs usually die a year after they have been diagnosed. Pain is usually the major grave companion to osteosarcoma in dogs. When in remission, pain management programs for the dog should be closely monitored with a special vet.
In case of cats, osteosarcoma is a lot less aggressive. It rarely affects body parts other than the rear legs and usually amputation alone saves the cat’s life. Like dogs, cats suffering from osteosarcoma are usually large, giant breeds of cats.
A far more serious bone cancer in cats is hemangiosarcoma. This sarcoma occurs in the endothelial cells lining the interior surface of the body’s blood vessels especially in the bones of the ribs or the limbs. Amputation is usually the definitive treatment method for hemangiosarcoma.
Palliative Care for Osteosarcoma patients:
An important part of osteosarcoma care is relieving the person’s symptoms and side effects of the drugs. This approach is called palliative care. Palliative care is defined as medical care that relieves pain, symptoms and stress caused by serious, chronic illnesses such as cancer. For osteosarcoma, palliative care techniques include nutritional changes, relaxation techniques, physical therapy, counseling and even members of the healthcare team like doctors and nurses. In most cases palliative care is meant to help the patients and their families cope with the gravity of their condition.
Palliative care is especially important in case of children and teenagers coping with amputation. Learning to live with only one limb could be very difficult, especially in case of children who have to change the prosthetic limbs as they grow up. Palliative care is also crucial in case of dealing with side effects of chemo and the toxicity of some drugs used to treat cancer. Most teenagers and children have a negative view of their bodies after being diagnosed with cancer, so emotional support is the most important step for the patients and their families. Meeting with other osteosarcoma survivors proved to be of great help, especially in case of patients who underwent amputation. Feelings of resentment, worry, anxiety, depression and fear of discrimination should all be addressed.
Various cancer centers and institutes provide counseling and information services for those recently diagnosed or treated. Osteosarcoma patients and survivors won’t find it hard to work out how to deal with their illness, no matter how grave it is. No one chooses to have osteosarcoma, but some choose to make the best of this experience and use it as fuel to move forward, not stand by.