Before deciding on treatment options, your doctor will need to know the extent, or stage, of the multiple myeloma. Your doctor will look at the results of blood tests, X-rays or other imaging tests, and bone marrow tests to determine the stage of the cancer.
Your doctor may also schedule a positron emission tomography (PET) scan to help determine your stage. This test scans your entire body, so it is more helpful than a series of several different X-rays. The PET scan shows which parts of your body are using glucose rapidly. Glucose use is a sign of active, quickly dividing cells, such as multiple myeloma cells. For this test, you get injected with a small amount of radioactive glucose. Then you lie still on a table that is pushed into the PET scanner, which rotates around you, taking pictures.
The traditional system used to stage multiple myeloma is called the Durie-Salmon system. This system is not used as much now as it was in the past. It is based on four different factors:
The amount of abnormal monoclonal immunoglobulin in the blood or urine. Large amounts of are a sign that many malignant plasma cells are present and are making this abnormal protein.
The amount of calcium in the blood. High blood calcium levels are also related to advanced bone damage. Bone normally contains lots of calcium and bone destruction releases calcium into the blood.
The amount of bone damage seen on X-rays. Many areas of bone damage are a sign of an advanced stage of multiple myeloma.
The amount of hemoglobin in the blood. Hemoglobin is the part of the red blood cell that carries oxygen. Low hemoglobin levels are a sign that the myeloma cells take up a lot of the bone marrow and there is not enough space left for the normal marrow cells that make red blood cells.
There are three different clinical stages of multiple myeloma in the Durie-Salmon system. Stage I indicates the smallest amount of tumor, and stage III indicates the largest amount of tumor.
Stage I. X-rays and blood tests indicate that only a small number of myeloma cells are present in the body. Most people with this stage do not have symptoms. Your doctor may say that you have a low tumor burden at this stage.
Stage II. The myeloma cells have spread through the body a little bit. Your doctor may say that you have an intermediate tumor burden at this stage.
Stage III. X-rays and blood tests indicate that many cancer cells are present in the body. Your doctor may say that you have a high tumor burden at this stage.
A newer system now used by many doctors to classify multiple myeloma is the International Staging System. This system divides myelomas into three stages based only on the blood levels of beta-2 microglobulin and albumin.
Stage I. The beta-2 microglobulin level is less than 3.5 milligrams/liter (mg/L) and the albumin level is 3.5 grams/deciliter (g/dL) or higher.
Stage II. Neither stage I or III, meaning that either:
The beta-2 microglobulin level is between 3.5 and 5.5 (with any albumin level), or
The albumin is below 3.5 while the beta-2 microglobulin is less than 3.5
Stage III. The beta-2 microglobulin level is greater than 5.5.