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Osteosarcoma: A Childhood Tragedy
Osteosarcoma, also known as Osteogenic Sarcoma, is a form of musculoskeletal cancer that typically develops in teenagers, though it can strike at any age. It usually occurs when children are going through rapid stages of growth, and is the most common bone cancer affecting young people (Chen 2013). Death often results via pulmonary metastatic disease, which occurs when cancer spreads to the lungs (Mehlman, Cripe).
Do you know anyone with Osteosarcoma?
While it can occur in any bone, osteosarcoma tends to target the largest, fastest-growing ones, particularly the tibia, femur, and humerus (Chen 2013), usually on the bone’s growth plates. It is thought to form from primitive mesenchymal cells (Mehlman, Cripe), and starts in the bone’s osteoblast cells, which are the cells responsible for replacing old bone during remodeling. In a normal bone, osteoclasts resorb bone tissue while osteoblasts fill in the hole created. Osteosarcoma occurs when the osteoblasts become cancerous and divide rapidly, creating a tumor and eventually metastasizing (Cancer Center).
The most common symptom of osteosarcoma is pain in the afflicted bone, though a palpable mass can also be present (Cancer Center). Bone fractures are also common - the bone formed by the cancerous osteoblasts is not as strong as normal bone tissue (Chen 2013). Other symptoms include a history of swelling and trauma at the affected site and a decreased range of motion. Symptoms can be present for many weeks or months prior to diagnosis (Mehlman, Cripe).
Diagnosis & Prognosis
There are a variety of ways in which osteosarcoma is diagnosed. Plain radiography is helpful in determining the difference between a cancerous tumor and a bone cyst. Radionuclide bone scans along with CT or MRI is used to evaluate whether the tumor has metastasized. Specifically, CT scans may be used to assess the tumor’s extent and exact location before biopsies and surgical planning, while an MRI of the site is the best way of determining the extent of the disease (Mehlman, Cripe). If a tumor is found, biopsies are necessary to determine the type of bone cancer and if it is malignant. There are three different types of osteosarcoma: high, intermediate and low grade. High grades are, sadly, most often found in children and are the fastest growing, most fatal variety, while the intermediate and low grade osteosarcomas grow slowly and are not as worrisome (American Cancer Society).
Osteosarcoma occurs most often in black people as opposed to white, standing at 5.2 to 4.6 cases per million per year. It also appears more often in men than women by a similar margin, 5.2 to 4.5 per million. Teens are most susceptible - 8.3 to 8.9 per million. This is perhaps due to the rapid periods of skeletal growth over that period (Mehlman, Cripe).
There are multiple methods of determining stages of osteosarcoma, the simplest being the binary localized or metastatic system. Localized cancer hasn’t spread to distant structures and organs, and is further divided into resectable and non-resectable groups. Resectable tumors can be fully removed by surgery, the latter cannot. Metastatic osteosarcoma has spread to other parts of the body, typically the lungs, and is significantly more deadly. The five-year survival rate for localized osteosarcoma is 60-80%, while is it has metastasized the prognosis drops to a grim 15-30%. Factors positively affecting one’s prognosis include being female, younger, and the tumor being resectable and more distal to the body (American Cancer Society).
Treatment Options - Looking to the Future
In both metastatic and localized stages, chemotherapy is required to ensure that all remains of the cancer are eliminated and is the go-to initial treatment option. It is often followed by surgery to remove the tumor if possible, and, in some cases, amputation if the cancer has spread to nearby structures. Radiation therapy might follow if not all the cancer is removed or there is a high chance of it returning. Rehabilitation is vital if the patient is to regain use of the limb (American Cancer Society).
While radiation, chemo and surgery are fairly standard treatment options, they are not the only tools available to doctors. Scientists have recently discovered a biomarker of sorts - a protein that indicates how well a patient might respond to chemotherapy and allow them to determine if a more aggressive form of chemo or alternate treatments are necessary (Borys 2012).
Did you learn something new?
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Brian Murphy, John W. Bishop, and Andrew Horvai. "P16 Expression Predicts Necrotic Response among Patients with Osteosarcoma Receiving Neoadjuvant Chemotherapy." Human Pathology (2012): 1948-954. Print.
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Osteosarcoma in Dogs?
Interestingly, Osteosarcoma is also a common killer among Great Dane, Doberman, and German Shepherd dogs. It typically strikes at middle to late age (5+ years) and manifests in lameness and swelling, along with extreme pain. There’s aren’t many treatment options and a positive diagnosis is usually a death sentence for your pet. Treatments that do exist carry significant complications and really aren’t cost-effective. With treatment, the median survival rate is only about year. Surprisingly, older dogs stick around for a bit longer on average (National Canine Cancer Foundation).
Osteosarcoma, like most cancers, is a nasty disease made more so by its primary target, children. With further research into biomarkers and other treatments, hopefully it can be stopped more frequently.