Osteosarcoma

What osteosarcoma is

Osteosarcoma forms in the growing ends of long bones (metaphyses), where bone is being actively made during adolescence. The tumor cells produce immature bone (osteoid). It most often affects:

• the lower end of the femur (thigh bone) near the knee
• the upper end of the tibia (shin bone) near the knee
• the upper end of the humerus near the shoulder

About half of cases occur around the knee. Less commonly it occurs in the pelvis, jaw or spine, especially in older adults.

Symptoms

• bone pain: often the first sign; may come and go at first, then become constant; often worse at night or with activity
• swelling or a lump over the bone, sometimes warm
• limping if the leg is affected
• reduced movement of the nearby joint
• fracture through a weakened bone after minimal trauma
• general symptoms such as tiredness or weight loss are less common unless the cancer has spread

Osteosarcoma vs growing pains

See growing pains. Pain in one place that persists for weeks, wakes a child, or comes with swelling needs an X-ray.

Causes and risk factors

Most osteosarcomas occur without a known cause. Risk factors include:

• rapid bone growth during adolescence
• previous radiation therapy
• inherited conditions: Li-Fraumeni syndrome, hereditary retinoblastoma, Rothmund-Thomson syndrome and others
• Paget's disease of bone in older adults
• bone infarcts and some benign bone conditions (rarely)

Injury does not cause osteosarcoma, though it may draw attention to an existing tumor.

Diagnosis

1. X-ray: often shows a destructive area with new bone formation and a "sunburst" pattern.
2. MRI of the whole bone to define the tumor's extent.
3. Biopsy: essential for diagnosis, ideally performed at the specialist center that will do the surgery, to avoid compromising limb-sparing options.
4. Staging: CT of the chest (the lungs are the most common site of spread), and a bone scan or PET-CT.
5. Blood tests: alkaline phosphatase and LDH may be raised and help with prognosis.

Treatment

Treatment is delivered by a specialist sarcoma team.

Chemotherapy

• Neoadjuvant chemotherapy (before surgery) for about 10 weeks shrinks the tumor and treats microscopic spread. The standard regimen for young patients is MAP: high-dose methotrexate, doxorubicin and cisplatin.
• Adjuvant chemotherapy after surgery completes treatment, over several months in total.
• The tumor's response to chemotherapy (the proportion of dead tumor cells after surgery) is an important predictor of outcome.

Surgery

• Limb-sparing surgery removes the tumor with a margin of healthy tissue and reconstructs the bone with a metal endoprosthesis, bone graft or both. It is possible in most people.
• Amputation may be needed if the tumor involves major nerves or blood vessels. Rotationplasty is an option for some young children.
• Surgery for lung metastases can be curative when the number of spots is limited.

Radiotherapy

Osteosarcoma is relatively resistant to radiation, so it is used mainly when surgery is not possible.

Outlook

• Localized disease: about 65 to 75% of people survive 5 years or more.
• Metastatic disease at diagnosis: about 20 to 30%, higher if lung spots can be completely removed.

Long-term follow-up monitors for recurrence and late effects of treatment, including heart problems from doxorubicin, hearing loss from cisplatin, kidney effects, fertility issues and prosthesis complications.

Frequently asked questions

What are the first signs of osteosarcoma?

The first sign is usually bone pain, often near the knee or shoulder, that persists, gets worse and may be worse at night. Swelling, a lump, limping, or a fracture after minor injury may follow.

Who gets osteosarcoma?

It mostly affects teenagers and young adults, especially during growth spurts, with a smaller peak in adults over 60. Inherited conditions such as Li-Fraumeni syndrome and previous radiation therapy increase the risk.

What is the survival rate for osteosarcoma?

For osteosarcoma that has not spread, about 65 to 75% of people survive at least 5 years. If it has spread at diagnosis, survival is lower, around 20 to 30%, though some are still cured.

Can you keep your leg with osteosarcoma?

In most cases, yes. Limb-sparing surgery with a metal implant or bone graft is possible for most people. Amputation is needed when the tumor involves major nerves or blood vessels.