Cancer primitif des os

Understanding bone

Bone is a living tissue. The hard bone tissue is made of tough, elastic fibres (collagen fibres) and gritty, hard material (minerals). 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) dissolves (resorbs) 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).

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

• Primary bone cancer is a cancer that starts in the bones. It is a rare type of cancer. It accounts for only two in every 1,000 cancers diagnosed. It affects males more frequently than females.

• Secondary (metastatic) bone cancer is a cancer which started in another part of the body and has spread to a bone. Many types of cancer can spread to the bone. Most commonly, cancers of the breast, prostate, lung, rein et thyroïde. Secondary bone cancer is common. The behaviour, treatment and outlook of secondary types of primary bone cancers are often quite different to primary bone cancer.

• Cancers of blood cells that originate in the bone marrow are not classified as bone cancers. Examples include: la leucémie, lymphoma et le myélome.

See the separate leaflet called Cancer for more information about cancer in general.

The rest of this leaflet is only about 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 supporting tissues (connective 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 affects almost 600 people a year in the UK. It arises from bone-forming cells. 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

The cells of this cancer look different to the more common osteosarcoma. It affects less than one person in a million each year. It affects around 25 children a year in the UK. Most cases occur in young people aged between 10 and 20 years, but it can occur at any age. It most commonly affects the hips (pelvis) and long bones in the leg. Ewing's tumours can also affect soft tissues around bone.

Chondrosarcoma

This type of cancer arises from cartilage-forming cells. As well as occurring in the cartilage, a chondrosarcoma can affect any bone, or develop on the surface of a bone. Most cases occur in people between the ages of 30 and 60 years. It most commonly affects the pelvis, shoulder blade (scapula), ribs, and the bones of the upper parts of the arms and legs.

Autres

Other rare types of primary bone tumour include fibrosarcoma, leiomyosarcoma, malignant fibrous histiocytoma, angiosarcoma and chordoma. Giant cell tumours are benign (non-cancerous) tumours of bone.

A cancerous (malignant) 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 to treat other problems.

• Maladie osseuse de Paget. This is a disease of the bone which occurs in some older people.

• An osteochondroma (chondroma). This is a non-cancerous (benign) 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.

• Pain. The pain may be quite vague at first but gradually tends to become 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.

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:

• Une radiographie. Primary bone cancers often have a characteristic appearance on an X-ray.

• Des imagerie par résonance magnétique (IRM). This is useful to show the exact site and size of a tumour.

• A small sample (a bone biopsie) is removed for it to be examined under the microscope to look for abnormal cells. This can confirm if there is bone cancer and what type it is.

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

Grading means how abnormal the bone cells look under the microscope.

• 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 be slow growing 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.

Staging means how big the cancer is and how far it has spread.

Grading and staging are combined together to assess the severity of a bone cancer. The commonly used system for bone cancer is:

• Stage IA - the cancer consists of low-grade cells and is totally within the bone. There is no spread to other parts of the body.

• Stage IB - 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 IIA - the cancer consists of high-grade cells and is totally within the bone. There is no spread to other parts of the body.

• Stage IIB - 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 III - the cancer is any grade but has spread to other parts of the body.

The staging is important, as the treatment options and outlook differ depending on the stage of the cancer.

Sometimes other grading and staging systems are used. Your specialist will explain what system is being used and what this means for you.

See the separate leaflet called Stages of cancer for more details.

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.

• Le stade du cancer (la taille du cancer et s'il s'est propagé).

• Votre santé générale.

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, the aim of treatment is 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, the aim of treatment is 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, the aim of treatment is to ease symptoms only. This is called 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.

Chirurgie

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. Removal of a limb (amputation) 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 on the types of operation which can be done.

Radiothérapie

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. Voir la brochure séparée intitulée Radiothérapie pour plus de détails.

Radiotherapy is usually used in combination with surgery and chemotherapy. Radiotherapy is not usually used for osteosarcomas or chondrosarcoma, as they are not very sensitive to radiation.

Chimiothérapie

Chemotherapy is a treatment which uses anti-cancer medicines to kill cancer cells, or to stop them from multiplying. Voir la brochure séparée intitulée Chimiothérapie pour plus de détails.

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 any cancer cells which may have been left in the body.

It is difficult to give an overall outlook (prognosis). 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.