What is Bone Cancer?

Bone cancer is an abnormal, uncontrolled growth of cells that form a tumour within the bone or in the tissues near the bone. Most bone cancers are not cancerous. Causes of bone tumours include abnormal healing of an injury, inherited conditions and radiation therapy. It is referred to as a primary bone cancer when it originates from the bone and is called Secondary bone cancer when it has spread from a different organ system. Common symptoms include persistent bone pain, swelling or a palpable lump, and sometimes an unexplained fracture of bone. Early detection and diagnosis through imaging and tissue biopsy are crucial for effective treatment, which often involves surgery, chemotherapy, and radiation therapy.

Types of Bone Cancers

Primary Bone Cancer:

This is cancer that begins in the cells of the bone.

• Osteosarcoma - The most common type, it starts in the bone-forming cells and most often affects the long bones of the arms and legs.
• Ewing Sarcoma - A type of bone cancer that can also start in soft tissues, it is common in children and young adults.
• Chondrosarcoma - A cancer that starts in cartilage cells.

Secondary (Metastatic) Bone Cancer:

This type of cancer starts in another organ, such as the breast, prostate, or lung, and then spreads to the bone.

Stages of Bone Cancer

According to the American Joint Committee on Cancer, the American Joint Committee on Cancer (AJCC) TNM system is a widely used staging system that combines the tumour size (T) and grade, extent in terms of spreading to the nearby lymph nodes (N), and if there is a spread to other parts of the body known as metastasis (M) to determine the stage and the grade of the cancer based on evaluating the tumour under the microscope. Numbers or letters after T, N, M, and G provide more details about each of these factors. Higher numbers generally mean the cancer has more concerning features.

Once T, N, M, and G categories have been determined, the TNM is combined in a process called ‘staging’ to arrive at an overall stage. These stages are described by Roman numerals from I to IV (1 to 4), and are sometimes divided further (Ia, Ib, etc).

There are other staging systems such as MSTS (Enneking) Tumour Staging used by the oncologists treating bone cancers.

Causes for Bone Cancers

While the exact cause of most primary bone cancers is unknown, certain risk factors may play a role in bone cancers such as certain genetic syndromes, past cancer treatments, and other bone conditions. Like in most cancers, bone cancer develops when changes in a cell's DNA cause it to grow and multiply uncontrollably, forming a tumour.

Symptoms of Bone Cancers

Symptoms can vary but often include the following:

• Pain in affected bone that persists and worsens over time, especially at night or during rest.
• Swelling or a lump near the affected bone.
• Unexplained tiredness.
• Fractures from a minor injury.
• Other symptoms such as fever, unexplained weight loss, and nerve symptoms when the tumour compresses a nerve.

Bone cancer isn't common, but it can affect any bone in the body. It most often occurs in the pelvis or the long bones in the arms and legs. Bone cancer can begin in the bone itself (primary bone cancer) or spread to the bone from another part of the body (secondary bone cancer).

Screening, and Diagnosis

Since bone tumours are rare, there is no routine screening test that are recommended, Symptoms and the results of physical exams and imaging tests might suggest that a person has bone cancer. Diagnosis typically starts with an X-ray for suspected bone issues, followed by more detailed imaging like MRI, CT scans, bone, or PET-CT scans to assess the extent of the abnormality and potential spread. A biopsy is essential for a definitive diagnosis to confirm the presence and type of cancerous cells. Blood tests are also advised to check overall health and for any specific biomarkers.

Treatment

Once a diagnosis of bone cancer is made, the cancer care team comprising of Ortho Oncologist, Radiation Oncologist, and Medical Oncologists will discuss your treatment options and weigh the benefits of each treatment option against the possible risks and side effects. The primary treatment approach is often surgical removal of the tumour which may involve procedures such as organ preserving surgery, or amputation and reconstructive surgery. Chemotherapy and radiation therapy are also used, sometimes in combination with surgery, to destroy cancer cells based on the type of bone cancer, which bone it started in, its stage (extent), and other factors. Chemotherapy involves use of medications to treat cancer which are administered through blood vessels to reach and destroy cancer cells anywhere in the body. This is useful for cancers that have spread to other organs. However, certain bone cancers such as Chordomas and Chondrosarcomas are not sensitive to chemotherapy for which other treatment options and medications are tried. Chemotherapy is very useful in treating cancers such as Ewing sarcoma, osteosarcoma, and undifferentiated pleomorphic sarcoma. Advanced treatments such as Immunotherapy, Pembrolizumab and Interferon alfa-2b and targeted therapies such as Imatinib, Erlotinib, Lapatinib and others are used in the treatment of bone cancers. Radiation treatment may comprise of linear accelerator treatments such IMRT (Intensity Modulated Radiation Therapy) or SRS (Stereotactic Radiosurgery) or Proton Therapy. Physical therapy is offered by a physiotherapist which includes treatments to manage pain, support psychologically, and restore muscle strength and functions. This plays an important role in all stages of treatment.

Survival Rate

Several factors such as type, age of the patient, if the cancer is localized or spread to other organs, grade and size of cancers in addition to factors such as the location of the tumour influence the prognosis. The oncologist is familiar with the specific cases he/she is treating and is the best source for questions about prognosis and survival.