Smoldering multiple myeloma is an early form of multiple myeloma. You might hear your doctor call it asymptomatic, which means it isn’t causing symptoms. It’s pretty rare.
It does cause you to have high numbers of plasma cells in your bone marrow and a high level of a certain type of protein called M protein in your blood and urine.
Smoldering multiple myeloma is similar to a disease called monoclonal gammopathy of undetermined significance (MGUS). People with both diseases may go on to develop multiple myeloma with symptoms. But if you have smoldering multiple myeloma, your risk of getting multiple myeloma within 5 years is much higher than if you have MGUS.
What Happens in Smoldering Multiple Myeloma?
Smoldering multiple myeloma isn’t yet cancer. It’s precancer. But it may get worse and become multiple myeloma, which is cancer.
Smoldering multiple myeloma causes these changes:
- Levels of monoclonal protein (M protein) in your blood that are 3 milligrams or higher
- Levels of plasma cells in your bone marrow, where your red blood cells are made, that are 10% or higher
You won’t have symptoms of multiple myeloma, which can include:
- Kidney damage
- Loss of kidney function
- High levels of calcium in your blood from damaged bone
- Bone lesions
Smoldering multiple myeloma often slowly gets worse. The number of plasma cells in your blood may be stable at first and then grow. Damage to your kidneys or bones could start, but it’s too slight to notice right now.
Smoldering multiple myeloma can raise your risk of these health problems:
- Peripheral neuropathy, which causes numb or tingling hands or feet
- Osteoporosis, or brittle bones
Causes and Risk Factors
We don’t really know what causes smoldering multiple myeloma or multiple myeloma. But doctors do have some ideas:
- Genes. If you have genes with certain mutations, you may make a higher number of plasma cells in your blood. The defective gene may switch on this process. It may also run in some families.
- Age. This is a common risk factor for smoldering multiple myeloma. It often develops between 50 and 70.
- Gender. Men are slightly more likely to get any type of myeloma than women.
- Race. It’s also twice as common in African-Americans as in whites.
- Obesity. People who are overweight or obese are at higher risk for myeloma.
How Is It Diagnosed?
Your doctor may notice signs of SMM on lab tests you take for any reason. Your blood or urine test may show high levels of M protein. Or you may have a blood test that shows high levels of plasma cells.
The results they’re looking for are:
- Blood monoclonal M protein of more than 3 g/dL
- 10% to 60% clonal bone marrow plasma cells
- No evidence of end-stage organ damage
- C= high calcium levels
- R = kidney problems
- A = anemia
- B = bone damage
Blood tests to diagnose smoldering multiple myeloma include:
- Serum protein electrophoresis
- Complete blood count
- Tests to measure serum calcium and creatinine levels
Urine test. Your doctor may need to collect your urine over a 24-hour period when you are diagnosed and again 2 to 3 months later as a follow-up.
Bone marrow biopsy. Your doctor will use a needle to collect some of the spongy stuff in the middle of your bone. The lab will check to see if there are myeloma cells in your bone marrow.
Skeletal survey. This series of X-ray takes a record of all the bones in your body. It can help the doctor spot anything abnormal.
MRI. Your doctor may also take an MRI scan of your spine and pelvis to look for any lesions or damage. MRI works better than X-rays to pick up signs of bone damage that may be getting worse.
You may not need any treatment for smoldering multiple myeloma. Your doctor will just watch you to see if your disease progresses to multiple myeloma.
Watchful waiting. Even if you still don't have symptoms of multiple myeloma, your doctor can look at your blood plasma cells under a microscope to see if there are any unusual changes. Another clue is a high level of M protein in the blood or urine. These are signs that you’re at high risk to get active multiple myeloma.
Chemotherapy . If you’re at high risk for active multiple myeloma, your doctor may prescribe a chemotherapy drug, lenalidomide (Revlimid), and dexamethasone. These treatments may help you prevent complications and live longer.
Immunotherapy. This new type of treatment for smoldering multiple myeloma is in clinical trials. These drugs use your body’s immune system to fight cancer.
Current clinical trials include medications that might slow the progression of this disease:
- Daratumumab (Darzalex) and isatuximab (ISA)
- Pembrolizumab (Keytruda)
There’s no way to prevent smoldering multiple myeloma. While you can change some risk factors like obesity by losing weight, this disease most likely results from a defective gene.