Multiple myeloma is a kind of bone marrow cancer. It is caused by the uncontrolled growth of a type of white blood cell known as plasma cells. Plasma cells make antibodies called immunoglobulins to fight infections.
In multiple myeloma, cancerous plasma cells multiply rapidly in the bone marrow. They eventually invade the outer layers of the bones. This can weaken bones so much that even a small injury can cause a bone to break.
The cancerous plasma cells also make a lot of immunoglobulins. This can cause the blood to become thick and sticky, and lead to the formation of blood clots. At the same time, blood levels of other antibodies drop, leaving the person open to infections.
Other problems that occur in people with multiple myeloma include
- a high blood calcium level, which can lead to dehydration, constipation, and confusion
- a decrease in kidney function
- a decrease in red blood cells (anemia)
Multiple myeloma is an uncommon cancer. It tends to occur in older people. Risk factors include exposure to
- a toxic chemical called benzene
At first, multiple myeloma does not cause any symptoms. But as it gets worse, symptoms can include:
- bone pain, often in the back and ribs
- marked fatigue
- easy bruising
- loss of appetite
- nausea and vomiting
Several types of tests are usually needed to diagnose multiple myeloma.
Blood tests. The amount of protein in the blood is measured. A high level of protein is a sign that plasma cells are making large amounts of immunoglobulin. The number of red blood cells is also measured. A low red cell count, anemia, occurs when plasma cells crowd the bone marrow and prevent it from making red blood cells.
Urine test. The amount of protein in the urine may also be tested.
X-rays. Taking x-rays of long bones, the skull, and chest can detect bones weakened by multiple myeloma.
Bone marrow biopsy. This involves removing a small amount of marrow from a bone with a long needle. The bone marrow is then examined under a microscope. Plasma cells usually make up a small percentage of cells in bone marrow. Multiple myeloma is diagnosed if the biopsy shows more than 30% plasma cells.
After diagnosis, laboratory tests will determine the extent of the cancer, which is described in "stages." The stage is assigned based on protein and calcium levels, kidney function, and the presence of cancer in the bone:
Stage I — few cancer cells have spread through the body. There may not be any symptoms of the disease.
Stage II — a moderate number of cancer cells have spread through the body.
Stage III — a large number of cancer cells have spread through the body. At this stage, there may be anemia, high levels of protein and calcium in the blood, and more than three bone tumors.
Treatment is sometimes delayed until symptoms appear. When treatment begins, it can include
Chemotherapy. Several four- to six-week courses of chemotherapy, given over one to two years, has proven very effective in treating multiple myeloma. Most people improve with chemotherapy.
Bortezomib (Velcade). This cancer drug has been shown to be effective in treating people who have previously taken at least one other myeloma drug.
Bisphosphonates. This class of drug, often injected into a vein once a month, can help prevent broke bones and prolongs survival.
Immunoglobulins. Infusing immunoglobulins into a vein can help prevent serious infections.
Thalidomide or lenalidomide. These drugs may be taken alone or with other medicines to try to keep the disease from coming back.
Radiation therapy. This is used to treat painful tumors in bones.
Stem cell transplant. Stem cells are "unformed" cells that have the potential to become any type of cell. The transplanted stem cells develop into healthy new blood cells. Before a stem cell transplant, high doses of chemotherapy are used to kill the cancer cells. Stem cells are then transfused into the bloodstream. In an autologous stem cell transplant, the stem cells were taken from the person's body before chemotherapy. In an allogeneic stem cell transplant, the individual gets stem cells from a donor.
None of these therapies provide a cure, but they can control the disease or delay its return for years.
Overall, about one-third of people with multiple myeloma live more than five years. Those diagnosed when the disease is at an early stage may live longer.