Smoldering Multiple Myeloma: Progression Explained

Smoldering multiple myeloma (SMM) is a precancerous condition that increases plasma cells in your bone marrow and specific proteins in your blood. Many people with SMM do not have any of the symptoms of multiple myeloma, such as anemia, bone lesions, or kidney failure. Research suggests that about 50% of people with SMM will develop multiple myeloma within 5 years.

This article explains what SMM is, how it can progress, and what the outlook is for someone with the condition. It also looks at the diagnostic process, risk calculator, and treatment options for SMM.

SMM is a rare condition that is also known as asymptomatic myeloma. This is because most people with SMM do not have any symptoms.

If you have SMM, however, you will have:

• increased levels, more than 3 grams per deciliter, of a protein called monoclonal protein in your blood
• increased levels, more than 10%, of plasma cells in your bone marrow

People with SMM do not have the CRAB symptoms of multiple myeloma. These are:

• C = calcium in high levels
• R = renal failure
• A = anemia
• B = bone damage

SMM is not a type of cancer, but it can develop into cancer. If you have SMM, you have a high risk of developing multiple myeloma, which is a type of cancer.  

Having SMM does not necessarily mean that you will develop cancerous multiple myeloma. Sometimes, SMM can progress slowly and may not result in multiple myeloma.

Although there is currently no cure for SMM, if you are at high risk of developing multiple myeloma, your doctor will prescribe treatments to slow down the progression of the condition. This can stave off symptoms.

Learn more about multiple myeloma here.

According to the National Cancer Institute, there is a 50–60% chance that SMM will develop into multiple myeloma during the first 5 years after you receive a diagnosis.

The International Myeloma Foundation gives an alternative outlook. They say that a person with standard-risk SMM has the following rates of progression to active myeloma:

• 10% per year for the first 5 years
• 3% per year for the next 5 years
• 1–2% per year for the next 10 years

SMM is an asymptomatic condition. This means that it does not cause symptoms in most individuals. However, even if the condition does not cause symptoms, it can still cause malignant plasma cells to secrete proteins. Clinicians measure these proteins in your blood or urine.

Since you may not have any symptoms, your doctor may suspect SMM only as a result of blood tests that you have undergone for another reason.

Researchers are not completely sure what causes SMM. However, they suggest the following risk factors:

• Age: People most often develop SMM between the ages of 50 and 70 years.
• Sex: Males are slightly more likely to develop multiple myeloma than females.
• Race or systemic racism: The risk of multiple myeloma in Black people compared with white people is higher by twofold. This may be due to a variety of factors, including systemic racism in healthcare and society, that lead to higher incidences of underlying conditions and inadequate access to quality healthcare.
• Genes: Some gene mutations may lead to higher levels of plasma cells in your bone marrow.

SMM causes no symptoms. Your doctor may suspect SMM if a blood test that you undergo for a different reason shows high levels of M-proteins.

Depending on your test results, your doctor may ask for the following tests to reach a diagnosis.

• A complete blood count can count the number of red blood cells, white blood cells, and platelets.
• A chemistry profile can measure the levels of albumin, calcium, creatinine, and other substances.
• Antibody testing can involve immunoglobulin levels and antibody types (Ig type G or Ig type A).
• Serum protein testing can measure the number of M-proteins.

• Urinalysis can detect unusual levels of protein or cells in the urine.
• Urine protein levels can produce results from a 24-hour specimen of urine.
• Urine protein electrophoresis can determine the levels of proteins, including M-proteins, in the urine.

Bone marrow biopsy or aspiration can help clinicians examine a small piece of bone and bone marrow.

Read and print our multiple myeloma appointment guide here.

There are three models that your doctor may use to classify how likely your SMM is to develop into multiple myeloma. These models are the Mayo Clinic model, the Spanish model, and the

International Myeloma Working Group model.

The Mayo Clinic model analyzes the size of the M-proteins in your blood and the extent to which your bone marrow has been affected.

Depending on the results of your test, you will know if you are at low risk, intermediate risk, or high risk.

The Spanish model analyzes the number of unusual plasma cells in the bone marrow and checks the levels of specific antibodies.

This model is different from the Mayo Clinic model because it only takes into account people who have a high risk. The Mayo Clinic model can categorize people of all risk levels.

The International Myeloma Working Group model is a widely recognized, easily implemented, and more recently published model.

It takes into account new knowledge of biomarkers that predict risks of the progression of SMM to multiple myeloma. This equates to three criteria, leading to three possible categories of risk.

Standard care for SMM is close follow-up every few months. These appointments may involve imaging or certain types of treatments, depending on a person’s situation.

One 2014 study observed that many people with SMM have lesions on their spines.

The authors of a 2015 article point out that, thanks to advances in imaging testing, your doctor can start to monitor your progression accurately and suggest intervention before the CRAB symptoms appear. The article suggests offering people with high risk SMM the option to take part in clinical trials.

Testing for condition progression may involve:

• X-rays
• CT scans
• PET scans

The same 2015 article suggests administering bisphosphonate once per year. More frequent dosing every 3–4 months can be considered for some people at high risk of SMM.

SMM is a precancerous condition that increases plasma cells in your bone marrow and specific proteins in your blood. People often have no symptoms. If you have a blood test for another reason, M-proteins in your blood may be the first sign that you have SMM.

Your doctor will most likely not treat SMM. Instead, they will likely monitor its progression with frequent testing. In some cases, they may use oral medication.