Smoldering multiple myeloma (SMM) is an asymptomatic blood disorder that can progress to active multiple myeloma (MM), a type of blood cancer. Approximately 10% of people with SMM develop MM each year during the first five years after diagnosis, making careful monitoring crucial1 2. While some patients remain stable for years without symptoms, others may progress to symptomatic disease requiring treatment1 3.
Symptoms of Smoldering Multiple Myeloma
Smoldering multiple myeloma is typically asymptomatic, meaning it does not cause noticeable symptoms4 1. Patients usually learn of their condition incidentally during routine blood tests that detect abnormal plasma cells or monoclonal (M) proteins2 1. Unlike active multiple myeloma, SMM does not cause symptoms such as bone pain, anemia, or kidney problems1 5.
When SMM progresses to active multiple myeloma, symptoms may include:
- Bone pain due to bone lesions6
- Easy bruising and bleeding caused by bone marrow infiltration6
- Fatigue and anemia5
Because SMM itself does not cause symptoms, patients often feel well and may not be aware of their condition until laboratory tests reveal abnormalities1 2.
Causes and Risk Factors
Smoldering multiple myeloma arises from abnormal plasma cells in the bone marrow. Plasma cells normally produce antibodies to fight infections, but in SMM, these cells become clonal (genetically identical) and produce abnormal monoclonal proteins (M-proteins) 78. The exact cause of this abnormal plasma cell growth is not fully understood1 .
Risk Factors
Several factors increase the risk of developing SMM:
- Age: SMM prevalence increases with age, commonly diagnosed in people over 60 years old9 1.
- Sex: Men are more likely to develop SMM than women9 .
- Race: Black individuals have a higher incidence of SMM compared to other racial groups1 .
- Family History: Having relatives with multiple myeloma increases the risk of SMM1 .
Genetic changes such as chromosome translocations and alterations in chromosome number are observed in SMM and contribute to abnormal plasma cell behavior and M-protein production8 .
Diagnostic Process and Criteria
Diagnosing smoldering multiple myeloma involves a combination of laboratory tests, imaging studies, and bone marrow biopsy1 7. The condition is heterogeneous, with varying clinical outcomes depending on molecular and genetic features8 .
Key diagnostic criteria for SMM include:
- Serum M-protein level ≥3 g/dL or urinary M-protein ≥500 mg per 24-hour collection7 1.
- Clonal plasma cells in the bone marrow between 10% and 60% 71.
- Absence of myeloma-defining events such as anemia, hypercalcemia, bone lesions, or kidney damage1 .
Imaging tests such as whole-body low-dose CT, MRI, or PET scans are used to detect bone or organ involvement and to rule out active myeloma10 1. Bone marrow biopsy assesses the percentage of plasma cells and may include genetic testing to identify chromosomal abnormalities1 8.
| Diagnostic Test | Purpose | Criteria for SMM |
|---|---|---|
| Serum protein electrophoresis | Measures M-protein levels in blood | M-protein ≥3 g/dL7 1 |
| 24-hour urine protein test | Detects M-protein in urine | Urinary M-protein ≥500 mg/24h7 1 |
| Bone marrow biopsy | Assesses plasma cell percentage and genetics | Plasma cells 10–60% 71 |
| Imaging (CT, MRI, PET) | Detects bone lesions or organ involvement | No myeloma-defining lesions10 1 |
Treatment Options and Monitoring
The current standard of care for smoldering multiple myeloma is close observation, often called a "watch and wait" approach, especially for patients with low or intermediate risk1 11. Treatment decisions are guided by risk stratification models that identify patients at higher risk of progression to active myeloma1 12.
Watch and Wait Approach
- Regular monitoring of M-protein levels in blood and urine1 .
- Periodic bone marrow biopsies to assess plasma cell percentage1 .
- Imaging studies to detect early bone or organ damage10 1.
- Follow-up intervals typically every 3–6 months initially, which may be extended if the disease remains stable1 11.
This approach aims to delay unnecessary treatment and avoid drug toxicities while promptly detecting progression1 11.
Medications
For patients classified as high-risk SMM, early intervention with medications may be considered to delay progression to active myeloma13 1. Commonly used drugs include:
- Immunomodulatory agents: such as lenalidomide, which modulate the immune system to control abnormal plasma cells1 14.
- Monoclonal antibodies: such as daratumumab, targeting plasma cells to reduce tumor burden13 15.
- Combination therapies: combining immunomodulatory drugs with steroids or monoclonal antibodies to improve outcomes14 .
Recent clinical trials have shown that early treatment in high-risk patients can prolong progression-free survival and overall survival without significantly affecting quality of life13 14.
Clinical Trials
Ongoing clinical trials are investigating new treatment strategies for SMM, especially for high-risk groups14 . Some notable trials include:
- Testing daratumumab alone or combined with lenalidomide and dexamethasone14 15.
- Evaluating novel drug combinations aiming for deeper responses and possible cure13 16.
- Assessing immune cell profiles as biomarkers to predict treatment response14 .
Participation in clinical trials offers patients access to cutting-edge therapies and contributes to advancing knowledge about SMM management14 .
“Given recent data showing improved progression-free survival with early intervention in high-risk smoldering multiple myeloma (SMM), the current dilemma is focused on how these patients should be treated.”
— Morie A. Gertz, Mayo Clinic16
Prevention and Risk Reduction
Currently, there are no proven strategies to prevent smoldering multiple myeloma1 2. Management focuses on delaying progression to active myeloma through risk-adapted monitoring and early intervention when appropriate1 .
Key components of risk reduction include:
- Regular laboratory and imaging surveillance to detect changes early1 .
- Lifestyle adjustments such as a balanced diet, exercise, and avoiding smoking may support overall health, though direct effects on SMM progression are not established17 .
- Genetic and biomarker research aims to identify patients who might benefit from preventive therapies in the future13 8.
High-risk patients may receive early treatment to reduce the chance of progression, but this is balanced against potential treatment side effects1 .
Associated Health Conditions
Smoldering multiple myeloma is associated with an increased risk of developing related conditions, including:
- Multiple myeloma: SMM is a precursor to active myeloma, with about a 10% annual risk of progression in the first five years1 5.
- Amyloidosis: A condition where abnormal plasma cells produce excess proteins that deposit in organs, potentially causing damage18 1.
Regular monitoring helps detect these complications early, allowing timely intervention1 .
Daily Life and Management
Living with smoldering multiple myeloma involves regular medical checkups and lifestyle management to maintain health and monitor disease status1 2. Since SMM is asymptomatic, many patients continue normal activities but should be aware of symptoms that may indicate progression.
Recommended management steps include:
- Scheduling regular blood and urine tests to track M-protein levels1 .
- Undergoing periodic imaging and bone marrow biopsies as advised1 .
- Maintaining a healthy diet and exercise routine to support overall well-being17 .
- Avoiding infections and protecting immune health2 .
- Seeking emotional support to manage anxiety or distress related to the diagnosis1 .
Multiple myeloma is a malignancy (cancer) often associated with symptoms such as anemia, hypercalcemia, and renal (kidney) failure. Smoldering multiple myeloma has many features of malignancy but is asymptomatic, so people often do not know they have it5 .
Common Questions Answered
Can smoldering multiple myeloma cause symptoms?
No, SMM is usually asymptomatic. Symptoms typically appear only if it progresses to active myeloma4 1.
What is the risk of progression to multiple myeloma?
The risk is about 10% per year during the first five years after diagnosis, decreasing thereafter1 2.
Do all patients with SMM need treatment?
No, many patients are monitored without treatment unless they are classified as high risk or show signs of progression1 11.
How often should patients with SMM be monitored?
Initially, every 3–6 months, with intervals possibly extended if the disease remains stable1 11.
Are there ways to prevent SMM from progressing?
No proven prevention methods exist currently, but early treatment in high-risk cases may delay progression1 13.
Can lifestyle changes help manage SMM?
Healthy lifestyle habits support overall well-being but have not been proven to prevent progression17 1.
