Bone cancer can occur in any bone in our body. It begins when the healthy cells in the bone grow uncontrollably and form a mass called tumor. There are mainly two types of bone cancer:

• Primary bone cancer — cancer that starts in the bone.
• Secondary bone cancer — cancer that starts in another part of the body and spreads to the bone (metastatic bone cancer).

What is a primary bone cancer?

Primary or true bone tumor develops when cells within a bone divide out of control forming a lump or mass of abnormal tissue. As the tumor develops, abnormal cells will displace healthy ones. These tumors will weaken the bone and make it vulnerable to fracture. A bone tumor can be cancerous (malignant) or non-cancerous (benign). Benign tumors are common and do not spread to other parts or destroy the bone tissues. Malignant tumors will spread to other body parts and are a threat to life. The malignant bone tumors are less common than benign bone tumors.

What are the types of primary bone cancer?

There are different kinds of primary bone cancer which are named based on the part of the bone or tissue that is affected and the kind of cells forming the tumor. The types include:

Multiple myeloma: It is a malignant tumor of bone marrow (the soft tissue that produces blood cells). It originates in the plasma cells of the bone marrow and destroys the bone completely.

Osteosarcoma: This type is formed from the bone-forming cells called osteoblasts in osteoid tissue (immature bone tissue). Though osteosarcoma can occur in any bone, it is more common near the shoulder and knee area. It can grow quickly and spread to other body parts including the lungs. Osteosarcoma is more common in children and adolescents and rarely occurs in older adults.

Ewing's sarcoma: This cancer arises more commonly in the bones of pelvis, legs, or ribs. Ewing’s sarcoma spreads quickly to other parts of body, including lungs. The risk of Ewing’s sarcoma is highest in children and adolescents.

Chondrosarcoma: This is a primary tumor of bone that usually starts in cartilage cells. Chondrosarcoma may occur around the hip, pelvis, or shoulder area. Middle-aged and older adults are more likely to develop this cancer.

What are the causes and risk factors of primary bone cancer?

The exact cause of bone tumor is unknown. A few possible causes are genetics (family history), previous radiation treatments, treatment with certain anticancer drugs and some injuries to the bones.

Other risk factors that may cause primary bone cancer include:

• A prior history of other cancers like breast, lung, prostate, kidney, or thyroid cancer.
• Paget's disease (a noncancerous bone condition).
• Injury to a bone causing chronic infection.
• Some inherited conditions such as:
  • Retinoblastoma (eye cancer that begins in the retina)
  • Li-Fraumeni syndrome (an inherited familial disorder due to a small change in a tumour suppressor gene known as TP53)
  • Rothmund-Thomson syndrome (a rare condition characterized by abnormalities of the skin, hair, eyelashes, eyebrows)
  • Werner syndrome (hereditary condition associated with premature aging).
• Males are more likely to develop bone tumor like osteosarcoma than females.
• Race is also a risk factor of primary bone cancers. Multiple myeloma is common in blacks, while Ewing sarcoma is more common in whites than in blacks or Asians.

What are the symptoms of primary bone cancer?

A dull and aching pain which may worsen at night or while doing any activity is the most common symptom of primary bone cancer. Tumors can also cause night sweats and fever. In certain cases, the symptoms will be undiscovered as the signs may seem like the pain of an existing injury that have already affected the bone. Sometimes there may be swelling at the site of the tumor.

How is primary bone cancer diagnosed?

As the signs and symptoms of bone tumor resemble to that of some infections, fractures or non tumor conditions, it is important to conduct a detailed evaluation of the patient. The diagnosis involves the following evaluation:

1. Patient history: As night pain is the only major symptom of bone tumors, your doctor will ask about prior cancer history, radiation exposure, Paget’s disease, fracture history and other symptoms.
   
   
2. Physical examination: Your doctor may perform a detailed physical examination to identify the tumor mass by checking for swelling or tenderness, presence of masses and any visible changes on the skin.
   
   
3. Imaging tests: Doctors will suggest imaging test to have a better diagnosis of the tumors.
   • X-rays will give dense images of the bones which helps to determine the size and location of the tumor.
   • A MRI scan will provide detailed pictures of the area suspected with tumor.
   • A positron emission tomography (PET) scan helps your doctor to locate the exact site of tumor.
     
     
4. Lab tests: Your doctor may order blood or urine test to help the diagnosis. A biopsy test is necessary to confirm the diagnosis of a bone tumor. In a biopsy, a sample of tissue is taken from the tumor and is examined to identify the abnormal cells in the given sample.

What are the treatment options for primary bone cancers?

The treatment options for primary bone cancers can be non-surgical and surgical methods. The treatment varies with the type of primary bone cancers. Here, the treatment options can be classified based on the nature on bone tumors.

• Benign tumors: If your tumor is benign, it may or may not require action, as these can grow, stay the same, or eventually disappear. Your doctor may closely monitor the tumor with routine imaging tests like x-ray to see the changes of tumor cells.
  In certain cases, your doctor may recommend removing the tumor (if it is spreading) to reduce the risk of fracture and other complications.
  
  
• Malignant tumors: If your tumor is malignant, treatment plan will include a team of doctors specialized in various domains like orthopedic oncologist, medical oncologist, radiation oncologist, radiologist, and pathologist. Treatment will depend on what type of bone cancer you have and its stage.
  Doctors often combine several methods to treat malignant bone tumors:
  
  
  1. Surgery: In this method, the entire tumor is removed, and surgeon will make sure no cancer cells are left after surgery. Common surgeries for malignant bone tumors are:
     • Limb salvage surgery is surgical method where the cancerous section of bone is removed but keeps nearby muscles, tendons, nerves, and blood vessels intact.
     • Amputation is the surgical method where a part or the entire limb (arm or leg) with tumor is removed.
       
       
  2. Radiation: It is used in combination with the surgical method, where high doses of x- rays are used to destroy the cancerous cells and to shrink the tumor. This will also reduce the pain and chances of future bone fractures.
     
     
  3. Chemotherapy: This treatment uses powerful chemicals to kill fast-growing cells in your body like cancer cells. Anticancer drugs are given intravenously (injected through the veins) or as pills (orally) to kill the rapidly growing cancer cells. Some side effects of chemotherapy are nausea, hair loss, weight loss and extreme fatigue.

What is the outlook or prognosis for primary bone cancer?

The outlook for survival of primary bone cancer varies with the type of cancer and the extent to which it has spread. The success of treatment depends on the type, site and the extent to which cancer has spread. Most of the cancer responds well to the chemotherapy and also for the surgical removal of cancer cells. If your tumor is benign, you’ll benefit from a regular follow-up as these bone tumors can reoccur and turn into cancer. Exciting advances are paving the way to better treatments for cancer and possibly more cures. However, more than 75% of people who have primary bone cancer have lived at least 5 years after diagnosis.^[4]

Is it possible to prevent primary bone cancer?

Since the exact cause of bone cancer is not known, there are no lifestyle changes or habits that can help in preventing bone cancer. Early detection offers the best chance for successful treatment of cancer. For those with a known risk factor, should get a regular health checkup.

Sources

1. Primary Bone Cancer. https://www.cancer.gov/types/bone/bone-fact-sheet. Accessed on:27-02-2020.
2. Bone tumor. https://orthoinfo.aaos.org/en/diseases--conditions/bone-tumor/. Accessed on: 27-02-2020.
3. Primary bone cancer. https://now.aapmr.org/primary-bone-tumors/. Accessed on: 27-02-2020.
4. https://www.cancerresearchuk.org/about-cancer/bone-cancer/survival. Accessed on 27-02-2020.