Bone cancer is a malignancy that forms in the cells of the bone. It comes in two forms: primary bone cancer, which starts in the bone itself, and secondary (metastatic) bone cancer, which spreads to the bone from a tumor elsewhere in the body. Primary bone cancer is uncommon, while secondary bone cancer is far more frequent in adults, since cancers of the breast, prostate, lung, and other organs commonly spread to bone tissue.
Understanding the distinction matters because the type of bone cancer determines the treatment approach, the outlook, and what symptoms to expect.
Types of Primary Bone Cancer
Three types account for the vast majority of primary bone cancers. They differ in which bone cells become cancerous and in who they tend to affect.
Osteosarcoma is the most common, making up about 36% of primary bone cancer cases. It develops in the cells that form new bone tissue and peaks between ages 10 and 30. It most often appears near the knee or in the upper arm, where bones are growing rapidly.
Chondrosarcoma is the second most common, accounting for 20 to 25% of cases. It arises in cartilage cells rather than bone-forming cells, and it primarily affects adults between 30 and 60. It tends to grow more slowly than osteosarcoma and often appears in the pelvis, upper leg, or shoulder.
Ewing sarcoma represents about 16% of cases. It most often strikes children and young adults and can develop in bone or in the soft tissue surrounding it. The pelvis, legs, and ribs are the most common sites.
Symptoms to Recognize
The hallmark symptom of bone cancer is pain at the tumor site. It often starts as a dull ache that comes and goes, then gradually becomes constant and more intense, especially at night or during activity. Many people initially assume it’s a sports injury or growing pain, which can delay diagnosis in younger patients.
Other common signs include swelling and tenderness near the affected area, unexplained weight loss, and persistent fatigue. In some cases, the tumor weakens the bone enough to cause a fracture from minor stress or a fall that normally wouldn’t break anything. A fracture through a weakened bone is sometimes the first indication that a tumor is present.
What Causes It and Who’s at Risk
Most bone cancers have no identifiable cause. However, certain inherited genetic conditions dramatically increase the risk, particularly for osteosarcoma. Li-Fraumeni syndrome, a rare inherited condition involving a mutation in a key tumor-suppressing gene, raises the relative risk of osteosarcoma roughly 107-fold. People with Li-Fraumeni syndrome face a 50% chance of developing some form of cancer by age 30, and osteosarcoma is diagnosed in about 12% of them.
Rothmund-Thomson syndrome, another rare genetic condition, is also strongly linked. In one review, osteosarcoma accounted for 62% of the cancers seen in affected patients, and a separate study found that 32% of patients with the syndrome developed osteosarcoma.
Prior radiation therapy is another established risk factor. Children treated with radiation for other cancers, particularly hereditary retinoblastoma, face up to a 400-fold increase in osteosarcoma risk compared to the general population. The risk is highest in bones that were within the radiation field.
How Bone Cancer Is Diagnosed
An X-ray is typically the first step when a doctor suspects a bone tumor. Bone cancers often produce visible abnormalities on X-ray, such as areas where bone appears eaten away or where new bone has formed in an irregular pattern. If something suspicious shows up, an MRI follows to provide a more detailed picture of the tumor’s size and its relationship to surrounding muscles, nerves, and blood vessels.
Imaging alone can’t confirm a cancer diagnosis. A biopsy is required, and it’s often performed using a needle guided by a CT scan so the doctor can precisely target the abnormal tissue. Getting the biopsy right is critical because the placement of the needle track can affect future surgical options, so it’s best done at a center experienced in bone tumors.
Treatment Approaches
Treatment for primary bone cancer almost always involves surgery, and the goal is to remove the entire tumor with a margin of healthy tissue around it. For tumors in the arms or legs, limb-salvage surgery is the preferred approach. This involves removing the cancerous section of bone and reconstructing it, often with a metal implant or bone graft, to preserve the limb’s function. Amputation is reserved for situations where the tumor can’t be fully removed while saving the limb.
Chemotherapy plays a major role in treating osteosarcoma and Ewing sarcoma. It’s given in two phases: before surgery to shrink the tumor and make it easier to remove, and again after surgery to target any remaining cancer cells. Surgery is typically scheduled within three weeks of finishing the pre-surgical chemotherapy, and post-surgical chemotherapy begins once the wound has healed, ideally within three weeks. Chondrosarcoma, by contrast, responds poorly to chemotherapy and relies more heavily on surgery alone.
Survival Rates by Stage
Outcomes vary significantly depending on the type of bone cancer and how far it has spread at diagnosis. Staging uses three categories: localized (confined to the bone where it started), regional (grown into nearby structures or lymph nodes), and distant (spread to the lungs or other bones far from the original site).
For chondrosarcoma, the five-year survival rate is 91% when localized, 71% when regional, and 28% when distant. The overall rate across all stages is 78%. Giant cell tumor of bone has a similar pattern: 91% localized, 88% regional, but drops to 39% once it has spread distantly. These numbers are based on patients diagnosed between 2015 and 2021.
Osteosarcoma and Ewing sarcoma generally carry lower survival rates than chondrosarcoma, especially at advanced stages, which is why early detection and aggressive treatment matter so much for these types.
Complications From the Disease
Bone cancer can cause problems beyond the tumor itself. Pathological fractures, where a bone breaks through a weakened spot, can happen with minimal trauma and often require surgical stabilization on top of cancer treatment.
High blood calcium, called hypercalcemia, is another significant complication. It occurs when tumor activity breaks down bone tissue faster than the body can regulate, releasing stored calcium into the bloodstream. This affects an estimated 40% of cancer patients at some point during their illness. Mild cases cause anxiety, depression, constipation, and reduced muscle strength. More severe cases lead to confusion, excessive thirst and urination, nausea, kidney problems, and in extreme situations, dangerous heart rhythm disturbances.
There’s also a destructive feedback loop at play in bone metastases. Cancer cells in the bone release substances that accelerate bone breakdown, and the breakdown of bone releases growth factors that fuel the cancer cells. This cycle worsens both the tumor’s growth and the bone destruction over time, which is why treatments that slow bone breakdown are an important part of managing bone-involved cancers.
Newer Treatment Directions
Standard chemotherapy has been the backbone of bone cancer treatment for decades, but newer strategies are showing promise. Immunotherapy, which helps the immune system recognize and attack cancer cells, is being tested in combination with other treatments. In one trial involving patients with a specific genetic subtype of advanced osteosarcoma, combining a targeted drug with an immunotherapy agent produced a response rate of 38.5%, compared to 13.3% with the targeted drug alone.
Researchers are also developing cancer vaccines designed to prime the immune system against proteins found on bone tumor cells. A trial comparing a specialized vaccine combined with immunotherapy against standard chemotherapy in primary osteosarcoma patients found that 56% of patients in the vaccine group had a major response, compared to 20% in the chemotherapy group.
Engineered immune cell therapies are another active area of investigation. Scientists are modifying donor immune cells to target specific markers on osteosarcoma cells, and early-phase trials are now recruiting patients to test these approaches. While these treatments are not yet standard care, they represent a meaningful shift in how bone cancer may be treated in the coming years.