What Is Osteosarcoma? Orthopaedic Oncologists Explain.

Advanced surgical techniques are improving outcomes for patients with this rare, aggressive cancer.

Osteosarcoma, also called osteogenic sarcoma, is the most common primary type of bone cancer. It develops in the cells that form our bones, leading to bone destruction and the potential to spread to other parts of the body.

Osteosarcoma is both an aggressive and highly rare cancer. The American Cancer Society says only about 1,000 new cases are diagnosed in the United States each year. Innovative treatment options have significantly improved surgical techniques, providing patients with better opportunities for recovery of their function.

“In the 1970s, osteosarcoma patients were treated with amputation, and survival rates were only about 20%,” says J. Dominic Femino, MD, an orthopedic oncologist and chief of the USC Musculoskeletal Oncology Center, part of Keck Medicine of USC. He is also co-leader of the USC Sarcoma Program, which unites Keck Medicine specialists from both USC Orthopaedic Surgery and the USC Norris Comprehensive Cancer Center.

“The combination of surgery and chemotherapy has increased survival to about 70%,” Dr. Femino adds. “It also allows us as orthopedic oncology surgeons to salvage limbs about 90% of the time, instead of doing amputations. So, osteosarcoma has had a nice success story.”

What causes osteosarcoma?

Teenagers develop osteosarcoma more often than adults, but the disease can occur at any age. According to the National Institutes of Health (NIH), about 75% of new diagnoses are in patients younger than 25. Patients are most likely to develop tumors in the knee, hip, shoulder or pelvis. 

The exact cause of osteosarcoma is unknown. While certain genetic disorders including Li-Fraumeni syndrome, hereditary retinoblastoma, Rothmund-Thomson syndrome and Bloom syndrome can increase the odds of bone cancer, experts say most patients have no identifiable risk factors before diagnosis.

“There are lots of different types of DNA mutations that can lead to osteosarcoma, and there can be multiple types of genetic mutations in one tumor,” Dr. Femino says. “It is a disease that does not have just one specific cause.” 

Dr. Femino adds that certain conditions such as Paget’s disease or fibrous dysplasia are associated with an increased risk of osteosarcoma in late adulthood. While rare, it is also possible for patients to develop osteosarcoma if they have previously undergone radiation treatment for another type of cancer.

How fast does osteosarcoma spread, and how is it diagnosed?

Osteosarcoma spreads through the bloodstream. In most cases, the cancer has already entered the bloodstream by the time the patient is diagnosed — although it may not initially show up on screening tests, which is why chemotherapy is essential. When it does metastasize, it most often spreads to the lungs.

Part of the problem is that osteosarcoma symptoms can be mistaken for sports injuries or as growing pains, says Lee Zuckerman, MD, an orthopedic oncologist with the USC Sarcoma Program who specializes in treating musculoskeletal tumors in adults and children.

Symptoms include persistent bone or joint pain that gets worse at night and does not go away with rest. Dr. Zuckerman advises parents, “If your child is limping, complaining of pain often or if you notice a lump forming on one side of their leg or arm, those are warning signs to get checked out.”

Osteosarcoma is usually first detected with an X-ray, followed by an MRI. A biopsy is then performed to confirm the diagnosis. A CT scan looking at the lungs, and a bone scan to look at other bones, helps determine whether the cancer has spread. 

How is osteosarcoma treated?

Osteosarcoma is typically treated with a combination of chemotherapy and surgery, although some low-grade tumors can be treated with surgery alone.

“The goal of surgery is to remove the tumor with a wide margin, which means we take out large segments of the bone and the normal tissue around it to ensure we get all the cancer cells,” Dr. Femino explains. “We then reconstruct the limb, oftentimes with a metal bone replacement. Sometimes we can use the patient’s native bone to regenerate new bone.”

Using the patient’s own bone to regenerate new bone is a relatively new technique performed after tumor resection, and the USC Sarcoma Program is one of only a few programs in the world that routinely performs and offers these procedures. Dr. Zuckerman notes, “These techniques can preserve the patient’s native joints and provide a reconstruction that is durable as it recreates the patient’s own bone.”

Although limb salvage has become the go-to treatment, sometimes amputation is chosen after careful conversation, says H. Paco Kang, MD, an orthopedic oncologist with USC Orthopaedic Surgery. “There are cases where amputations may allow for a better or quicker return to function, and some patients want to avoid some of the potential complications with large reconstructions,” he explains.

If an amputation is unavoidable, the USC Sarcoma Program offers advanced procedures that help maximize function and reduce pain. Dr. Zuckerman says a rotationplasty is one of the procedures he performs on younger patients. He rotates the leg around so that the ankle joint becomes the knee. “It allows the patient to have a below-the-knee prosthetic and can be very functional,” he says.

Another option is osseointegration, which involves connecting a patient’s prosthesis directly to the bone at the amputation site to enhance stability and balance. “This procedure is usually for patients who have had a previous amputation and are struggling with their prosthesis,” says Dr. Zuckerman. “Osseointegration is still relatively new, and the USC Sarcoma Program is one of the few places to offer it.”

“Osseointegration is also something we consider when patients are expected to have a short residual limb that creates prosthesis challenges,” Dr. Kang adds.

All three physicians encourage patients diagnosed with osteosarcoma to seek care at a dedicated cancer center like Keck Medicine. “Because of the rarity of these tumors, it is important to be treated by a multidisciplinary team, by oncologists and surgeons who are experts in this type of cancer and can give you all the various treatment options,” Dr. Kang says.

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