Understanding bone

Bone is a living tissue. The hard bone tissue is made of collagen fibres (tough, elastic fibres) and minerals (gritty, hard material). There are two main types of cells within the hard bone tissue that make and mould bone. One type (osteoblasts) makes and lays down bone material. Another type (osteoclasts) resorbs (dissolves) particles of bone. These cells are active throughout life. They work in a balanced way to make and mould bone, repair damage and keep the bone structure correctly 'woven'. There is a slow but constant turnover of bone. Chondrocytes are cells which make cartilage, the tissue that covers the ends of bones in joints.

In the centre of some larger bones is the soft bone marrow. This is where blood cells are made (red blood cells, white blood cells, and platelets).

What is cancer?

Cancer is a disease of the cells in the body. The body is made up from millions of tiny cells. There are many different types of cell in the body, and there are many different types of cancer which arise from different types of cell. What all types of cancer have in common is that the cancer cells are abnormal and multiply 'out of control'.

A malignant tumour is a 'lump' or 'growth' of tissue made up from cancer cells which continue to multiply. As they grow, malignant tumours invade into nearby tissues and organs which can cause damage.

Malignant tumours may also spread to other parts of the body. This happens if some cells break off from the first (primary) tumour and are carried in the bloodstream or lymph channels to other parts of the body. These small groups of cells may then multiply to form 'secondary' tumours (metastases) in one or more parts of the body. These secondary tumours may then grow, invade and damage nearby tissues, and spread again.

Some cancers are more serious than others, some are more easily treated than others, some have a better outlook (prognosis) than others.

So, cancer is not just one condition. In each case it is important to know exactly what type of cancer has developed, how large it has become, and whether it has spread. This will enable you to get reliable information on treatment options and outlook.

What is bone cancer?

Bone cancer can be divided into primary bone cancer and secondary bone cancer.

• Primary bone cancer means that the cancer started (originated) from cells in the hard bone tissue. It is a rare type of cancer. It accounts for only two in every 1000 cancers diagnosed. It affects males more frequently than females.
• Secondary (metastatic) bone cancer means that a cancer which started in another part of the body has spread to a bone. Many types of cancer can spread to the bone. Most commonly, cancers of the breast, prostate, lung, kidney and thyroid. Secondary bone cancer is common. The behaviour, treatment and outlook of secondary bone cancers is often quite different to primary bone cancer.
• Cancers of blood cells that originate in the bone marrow are not classified as bone cancers. For example, leukaemia, lymphoma and myeloma.

The rest of this leaflet is only about primary bone cancer. See the separate leaflets for other types of cancer which may spread to one or more bones, and for information about leukaemias, lymphomas and myeloma.

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Types of primary bone cancer

There are different types of primary bone cancer. They are classified by the type of cell which occurs in the cancer. Most types of primary bone cancer end with ...sarcoma. A sarcoma is a cancer that originates from cells which occur in and make connective tissues (supporting tissues) of the body. For example, bone, muscle, cartilage, ligaments, etc.

Osteosarcoma

This is the most common type of primary bone cancer, but even this is rare. It only affects around 150 people a year in the UK. It arises from bone forming cells. Most cases occur in young people between the ages of 10 to 25, but it can occur at any age. It typically develops in the growing ends of the bone in young people, most commonly in bones next to the knee and the upper arms. However, any bone can be affected.

Ewing's sarcoma

This is named after the doctor who first described it in the 1920s. The cells of this cancer look different to the more common osteosarcoma. It only affects around 100 people a year in the UK. Most cases occur in young people between the ages of 10 to 20, but it can occur at any age. It most commonly affects the pelvis and long bones of the leg. However, any bone can be affected.

Chondrosarcoma

This type of cancer arises from cartilage forming cells. As well as occurring in the cartilage, a chondrosarcoma may also develop within a bone, or on the surface of a bone. Most cases occur in people between the ages of 40 and 75. It most commonly affects the pelvis, scapula (shoulder blade), ribs, and the bones of the upper parts of the arms and legs.

Other

Other rare types of primary bone tumour include fibrosarcoma, leiomyosarcoma, malignant fibrous histiocytoma, angiosarcoma and chordoma.

What causes primary bone cancer?

A cancerous tumour starts from one abnormal cell. The reason why a cell becomes cancerous is unclear. It is thought that something damages or alters certain genes in the cell. This makes the cell abnormal and multiply 'out of control'. In most cases of primary bone cancer it is not known why cells become cancerous. The most common types, osteosarcoma and Ewing's sarcoma, mainly occur in young people. The cause of these may have something to do with changes in the bone as it is growing.

In some cases, there is a known 'risk factor'. For example, your risk of developing a primary bone tumour is increased if you have:

• High dose radiotherapy for other problems.
• Paget's disease. This is a disease of the bone which occurs in some older people.
• An osteochondroma (chondroma). This is a benign (non-cancerous) bone tumour which occasionally turns into a chondrosarcoma.
• Certain rare inherited disorders including: Li-Fraumeni syndrome, hereditary multiple exostoses (HME), and hereditary retinoblastoma.
• Ollier's disease (enchondromatosis) - a rare bone condition.

There is no evidence that having a previous injury to a bone increases your risk of developing bone cancer in the future.

What are the symptoms of primary bone cancer?

• Pain. The pain may be quite vague at first, but tends to gradually becomes persistent and more severe over the affected part of the bone.
• Swelling over the affected part of the bone. (May only be noticeable with bones close to the surface of the skin.)
• Difficulty in moving a joint if the cancer is near to a joint.
• Pressure symptoms if the tumour grows from the bone and presses on nearby structures. For example, pressure on a nerve may cause pain, tingling, weakness of muscles, or numbness of an area of skin.
• A break (fracture) of a bone may occur at the site of the tumour after a minor injury.

General symptoms may occur as the cancer becomes larger. For example, tiredness, weight loss, sweats. If the cancer spreads to other parts of the body, various other symptoms can develop.

How is primary bone cancer diagnosed and assessed?

Initial assessment and diagnosis

If a doctor suspects that you may have primary bone cancer, you are likely to have a number of tests. These may include one or more of the following:

• An X-ray. Primary bone cancers often have a characteristic appearance on an X-ray.
• A bone scan. A bone scan involves an injection of a a small dose of radioactive material. This is taken up by active bone tissue. Cancerous bone tissue is very active and shows on a scanner as a 'hot spot'.
• MRI scan. This is useful to show the exact site and size of a tumour.
• A bone biopsy. A biopsy is when a small sample of tissue is removed from a part of the body. The sample is examined under the microscope to look for abnormal cells.

If you are confirmed to have primary bone cancer then further tests are usually advised to assess if the cancer has spread. This may include various blood tests, X-rays and scans.

Assessing the severity of the cancer - grading and staging

The results of the biopsy can show the type of the cancer. Also, by looking at features of the cells the cancer can be 'graded'. For primary bone cancers, two grades are used:

• Low grade - the cells look reasonably similar to normal bone cells. The cancer cells are said to be 'well differentiated'. The cancer cells tend to grow and multiply quite slowly and are not so 'aggressive'.
• High grade - the cells look very abnormal and are said to be 'poorly differentiated'. The cancer cells tend to grow and multiply quite quickly and are more 'aggressive' and are more likely to spread

The stage of primary bone cancer is based on the grade of the cancer, and how much it has grown or spread. The staging system commonly used is:

• Stage 1A - the cancer consists of low-grade cells, and is totally within the bone. There is no spread to other parts of the body.
• Stage 1B - the cancer consists of low-grade cells, but has grown through the wall of the bone. There is no spread to other parts of the body.
• Stage 2A - the cancer consists of high-grade cells, and is totally within the bone. There is no spread to other parts of the body.
• Stage 2B - the cancer consists of high-grade cells, but has grown through the wall of the bone. There is no spread to other parts of the body.
• Stage 3 - the cancer is any grade but has spread to other parts of the body.

The staging is important as the treatment options and outlook (prognosis) differ depending on the stage of the cancer. (See separate leaflet called 'Cancer - Staging and Grading' for more details.)

What are the treatment options for primary bone cancer?

The main treatments used for primary bone cancer are surgery, chemotherapy and radiotherapy. The treatment or combination of treatments advised in each case depends on various factors such as:

• The type of primary bone cancer.
• The exact site of the cancer.
• The stage of the cancer (how large the cancer is and whether it has spread).
• Your general health.

You should have a full discussion with a specialist who knows your case. They will be able to give the pros and cons, likely success rate, possible side-effects, and other details about the possible treatment options for your type of cancer. You should also discuss with your specialist the aims of treatment. For example:

• In some cases, treatment aims to cure the cancer. (Doctors tend to use the word 'remission' rather than the word 'cured'. Remission means there is no evidence of cancer following treatment. If you are 'in remission', you may be cured. However, in some cases a cancer returns months or years later. This is why doctors are sometimes reluctant to use the word cured.)
• In some cases, treatment aims to control the cancer. If a cure is not realistic, with treatment it may be possible to limit the growth or spread of the cancer so that it progresses less rapidly. This may keep you free of symptoms for some time.
• In some cases, treatment aims to ease symptoms ('palliative treatment'). For example, if a cancer is advanced then you may require painkillers or other treatments to help keep you free of pain or other symptoms. Some treatments may be used to reduce the size of a cancer which may ease symptoms such as pain.

Surgery

The types of operation vary depending on the type and site of the cancer. If the cancer is in an arm or leg, it is often possible to remove it with 'limb-sparing' surgery. This means surgery where just the affected part is removed, and is replaced with an artificial metal fitting (prosthesis) or a bone graft. Amputation (removing a limb) used to be the main operation, but this is done less often these days due to the improved surgical techniques with limb-sparing surgery. However, amputation is still needed in some cases, depending on the size, spread or site of the tumour. Your specialist will advise on whether surgery is possible, and the types of operation which can be done.

Radiotherapy

Radiotherapy is a treatment which uses high energy beams of radiation which are focused on cancerous tissue. This kills cancer cells, or stops cancer cells from multiplying. (See separate leaflet called 'Radiotherapy' for more details.)

Radiotherapy may be used as an alternative to surgery for Ewing's sarcoma. For example, if the tumour is in the spine when surgery is not possible. Radiotherapy is not usually used for osteosarcomas or chondrosarcoma as they are not very sensitive to radiation.

Chemotherapy

Chemotherapy is a treatment which uses anti-cancer drugs to kill cancer cells, or to stop them from multiplying. Chemotherapy may be given in addition to surgery or radiotherapy, depending on the type and stage of the bone cancer. This may be before surgery to shrink the size of the cancer so a smaller operation can then be performed. Chemotherapy may also be given after surgery or radiotherapy. This aims to kill to cancer cells which may have been left in the body. (See separate leaflet called 'Chemotherapy' for more details.)

What is the prognosis (outlook)?

It is difficult to give an overall outlook. Every case is different, and the success of treatment depends on the type, site and stage of the cancer - the earlier the stage, the better the outlook. In general, the outlook for primary bone tumours has improved in the last 10-20 years. This is due to improved surgical techniques and improved chemotherapy.

The treatment of cancer is a developing area of medicine. The information on outlook above is very general. New treatments, including gene therapy, are being investigated and may improve the outlook in the future. The specialist who knows your case can give more accurate information about your particular outlook, and how well your type and stage of cancer is likely to respond to treatment.

Further help and information

Bone Cancer Research Trust

Tel: 0113 262 1852 Web: www.bonecancerresearch.org.uk
Promotes research into the causes and treatment of primary bone cancer.

Macmillan Cancer Support

Tel: 0808 800 1234 Web: www.macmillan.org.uk
Provide information and support to anyone affected by cancer.

Cancer Research UK

Web: www.cancerhelp.org.uk provides facts about cancer including treatment choices.

Other support groups

See www.patient.co.uk/selfhelp.asp for a list of self-help and support groups.