Bone cancers occur when some cells in the bone grow and divide without control. It rarely occurs in adults and accounts for only one percent of all cancers. Your pelvic bone, long bones of the arms and legs, are the most common bone cancer sites.

In the bones, the cancerous cells clump together to form a tumor mass. Most of the bone tumors are benign and do not spread outside the bone. But, malignant bone tumors grow outside the bone and affect the muscles, cartilage, and other tissues close to it. It will also spread to other areas of the body.

The exact cause of bone cancers is not clear. But your risk of it is more if you have had radiation treatment in the past. 

Bone tumors may also occur due to the spread of cancer from other organs. These cancers, called secondary or metastatic bone cancers, will have the features of cancer of those organs from where it spread.

Pain or swelling in or around the bones is the most common symptom. Bone fractures without a cause may occur in late stages.

X-rays, CT, MRI, or PET scans will help to detect bone cancers. A biopsy will help to know the stage and type of cancer.

Surgery is the most common treatment for bone cancers. Some may need chemotherapy and radiation therapy, as well.

Common types of bone cancers

• Osteosarcoma: It is the most common type of bone cancer and usually affects the ends of the bones of the legs, thighs, and arms. The knee is the most common site of this cancer. Youngsters below the age of thirty are more at risk. It may spread to other organs quite fast. The main feature is the presence of a higher number of immature bone cells in the tumor.
• Chondrosarcoma: It affects the bones and the cartilages at the ends of the bone. The most common sites of this cancer are the shoulder, hips, and pelvis. The tumor will have larger numbers of cancerous cartilage cells than bone cells. Most common and early symptom is the stiffness of these joints. Those above the age of forty have a slightly higher risk.
• Ewing's sarcoma: It is a rare type of bone cancer that affects the bones and soft tissues like cartilages, nerves, etc. near it. Young adults and children are more at risk of this cancer. It usually begins in the pelvic or leg bones and rarely in the chest wall's soft tissues.

What causes bone cancer?

It is not clear as to what causes bone cancers.

Usually, your bone cells divide to produce more bone cells which grow to become healthy bone cells. The older cells die as new cells form in the bone. It is the genes in your bone cells that decide how they should divide and for how long to live.

Any changes in these genes will make the bone cells divide more and live longer than usual. It thus leads to cancer. These cells also destroy the nearby cells and spread around to form lumps or tumors in the bone. Some of these cells even move to other parts of the body to start cancers there. 

But what makes these genes change is not clear. But some factors can increase their risk.

Risk factors of bone cancer

Some of the common risk factors are

• Your age- Most bone cancers affect children and young adults below the age of thirty. So, it is one of those rare cancers, where your risk reduces as you age.
• Previous cancer treatments- If you have had radiation or chemotherapy in the past, you are more at risk
• Having benign tumors like Paget's disease- At times, these tumors can change their nature and become cancers.
• Children with eye cancer called retinoblastoma have a risk of getting some bone cancers.

Symptoms of bone cancer

Though there are different types of bone cancers, most of their general symptoms are almost the same. Some of these include

• Bone pain- It is the most common and early symptom. The pain will feel like a dull ache deep in the bone. At times, it will spread over an area, e.g., the hips or the pelvis. You will have more pain while you are active in the early stages. But later on, the pain will persist at rest as well.
• Swelling and tenderness over the bone- As the tumor grows in size, you will have a visible swelling over the area. It will be more if the cancer is in the joints. You will have pain if you touch it.
• Stiffness of the joint- If the tumor is at the end of the bone, you will have stiffness in that joint. The movement of the joint will cause pain, as well.
• Sudden fractures of the bones- As the tumor grows, it makes the bone weak leading to fractures.
• Fatigue- As the cancer advances in stage, you will feel tired for no reason.
• Sudden loss of weight- You will find that you are losing a lot of weight without trying to do so.
• Breathing problems- Bone cancers may spread to the lungs and create breathing issues.

Diagnosis of bone cancers

At times, bone cancers show severe symptoms only in the advanced stages. So bone or joint problems that do not respond to treatments will need a few tests to rule out cancers. It also helps to detect it quite early.

Bone scan- It uses a radioactive dye or tracer to know the structure of your bone. You will have the tracer as an injection through your vein, which moves towards the bone. The doctor will watch its movement on a screen. The healthy bone will look lighter, and the problem areas will look darker.

Biopsy of the bone- In this, the doctor will observe a bone sample under a microscope to look for cancer cells. It helps to find out the type and stage of cancer. The doctor will take the sample with the help of a needle or through a small surgery.

Blood tests- There will be an increase in the level of certain enzymes like alkaline phosphatase.

MRI, CT, and PET scans will show the exact location and the extent of cancer. It also helps to know whether cancer has spread or not.

Stages of bone cancer

• Stage 1 - Cancer remains in the bone and has not started spreading. 
• Stage 2 - Cancer has not spread yet, but it may become invasive. It will be a threat to any nearby tissues.
• Stage 3 - Bone cancer has spread to one or more areas nearby and has become invasive. 
• Stage 4 - This is the most severe stage of bone cancer. Cancer has spread to a larger area and distant organs as well.

Treatments for bone cancer

Treatment will depend on the type and stage of bone cancer.  

Surgery: Surgery is the most common treatment for bone cancers. Limb Salvage Surgeries are preferred. During surgery, the surgeon will remove the tumor and a safe margin of healthy bone around it. It is to make sure that there are no cancer cells left behind. 

The surgeon will take extreme care to keep as much as possible of healthy bone intact. After surgery, you will have metal implants or bone grafts to replace the missing bone.

In some cancers that affect the bones of the arms or legs, the surgeon will remove the part of it with cancer by amputation. By placing artificial limbs at its place, one can lead a normal life.

Surgery will give the best results at the early stages. Then the surgeon will have to remove only a small portion of the bone to remove the tumor. It helps to spare a lot of bone, helping it to function like normal.

Chemotherapy: It uses drugs to kill cancer cells. You will have to take them through an IV infusion or as pills. Some bone cancers respond to it better than others. You will have the treatment in 'cycles' with a few days of rest in between. There will be gaps in between the cycles to promote better tolerance to treatment.

Radiation therapy: It uses high-energy rays to destroy cancer cells. You will have the radiation from a machine kept close to your body, which targets the beams to the tumor. It will last for a minute or two. You will have the treatment for a few days at a stretch