Multiple myeloma

What is multiple myeloma?

Multiple myeloma occurs when there is an uncontrolled growth of abnormal plasma cells in the bone marrow. The name was introduced in 1873 to emphasise that multiple bone tumours are the main characteristic of the disease. Unlike leukaemia, where cancerous cells are found in the blood, the malignant plasma cells in myeloma do not usually leave the bone marrow. On the rare occasion this happens, the disease is referred to as plasma cell leukaemia. Sometimes a localised deposit of myeloma can occur outside the marrow and this is called a plasmacytoma.

Multiple myeloma is a disease of the middle-aged and elderly. It is very rare under the age of 30 and comprises about one per cent of all cancers. Symptoms vary depending on how advanced the disease is and none may be evident in the early stages.

A frequent symptom of myeloma is bone pain. Commonly, people experience back or ribcage pain, which is aggravated by movement. This may come on gradually or fluctuate in intensity for weeks or months before becoming continuous and disabling. Pain can also occur in other sites such as the upper arms or legs. The pain is due to the growth of the tumour within the marrow and is accompanied by a progressive destruction of the affected bones. This leads to the development of holes in the bones (lytic lesions) or generalised weakness (osteoporosis) of the bone, or both.

When myeloma is not associated with bone destruction, generalised disease may develop and progress without obvious symptoms. In this case, normal bone marrow cells are replaced by abnormal plasma cells and the marrow ceases to function properly. When red cells are reduced a person becomes anaemic. The production of white cells is also reduced and this, together with a reduction of normal antibodies, means people have a reduced ability to fight infections.

Causes

The cause of multiple myeloma is unknown. The only well-established risk factor is ionising radiation. Industrial and environmental factors, such as exposure to certain solvents and air borne particles, may encourage the emergence of abnormal plasma cells, eventually leading to the development of myeloma. However, no one factor has been identified as a strong cause.

Diagnosis

Multiple myeloma is thought to originate from the growth of a single cancerous (malignant) plasma cell. Since every cell in the tumour is identical and produces exactly the same antibody, this will appear in the blood or urine in excessive amounts and can be detected by special laboratory tests. This antibody is sometimes referred to as the paraprotein or monoclonal protein.

The antibody consists of two parts - a heavy chain and a light chain. When light chains are produced in excess, as is common in myeloma, they circulate in the blood and, unlike complete antibodies, are small enough to be excreted in the urine. The presence of antibody light chain in the urine was first described by Bence-Jones in 1850. And the appearance of the Bence-Jones protein in the urine is important in the diagnosis of multiple myeloma, as it is present in 80-90 per cent of patients who are found to have the disease.

In most cases, multiple myeloma is found by examining the bone marrow, using a test called a bone marrow biopsy. Diagnosis is confirmed by the presence of increased numbers of abnormal plasma cells in the bone marrow, together with bone damage and the detection of either a high concentration of a unique antibody in the blood (a monoclonal protein or paraprotein) or Bence-Jones protein in the urine.

A series of X-rays may also be taken to look at the number and size of tumours in the bones. Sometimes, magnetic resonance imaging (MRI) is used, particularly if there is concern about damage to the spine.

People with extensive bone damage may have increased amounts of calcium in their blood, called hypercalcaemia. If this is happening it can cause a loss of appetite, nausea, vomiting, dehydration, confusion and constipation. Excess calcium which is not excreted in the urine is deposited in the kidneys. This, together with the excretion of Bence-Jones protein, can lead to kidney failure.

Often people might not show any of the major symptoms of multiple myeloma, but just have small amounts of an abnormal protein in the blood and a small excess of myeloma cells in the bone marrow, which is called smouldering myeloma.

Treatment

Multiple myeloma usually progresses slowly but rapid deterioration can also occur over a short time.

The way in which it is treated depends on how extensive the disease is and how much damage has occurred by the time it is diagnosed. A series of tests, which look for abnormalities in the myeloma cells, can help determine how quickly it is likely to progress.

The exact form of treatment is determined by age, the extent of the myeloma and the number of complications that have occurred. People who do not have any symptoms when their myeloma is diagnosed may not need immediate treatment. In this situation the patient's clinical symptoms and laboratory tests are monitored closely, as therapy will eventually be necessary.

People with active or symptomatic myeloma are generally treated with chemotherapy. In younger patients, high dose chemotherapy may also be offered with a stem cell transplant. Radiation therapy may also be used to help control some of the symptoms associated with myeloma.

Presently, the treatments for myeloma do not offer a cure, although there is a high likelihood that the disease can be controlled.

For more information on this disease, or a copy of our information booklet on multiple myeloma, please contact lbf@leukaemia.org.nz or 0800 15 10 15.