Smoldering Myeloma Treatment: Best Approaches and Strategies

Smoldering myeloma sits in a frustrating middle ground: it is not the harmless precursor condition known as MGUS, but it is not yet active multiple myeloma requiring immediate chemotherapy. For decades, the standard approach was simply to watch and wait. That picture has shifted considerably, with clinical trials now showing that early treatment in higher-risk patients can cut the chance of progression roughly in half, and the first drug (daratumumab) recently earning regulatory approval specifically for this condition. Still, not every person with smoldering myeloma benefits from treatment, and distinguishing those who do from those who can safely be monitored remains the central challenge.

What Smoldering Myeloma Actually Is

Smoldering multiple myeloma (SMM) is defined by having between 10 and 60 percent clonal plasma cells in the bone marrow, or a serum M-protein level of 3 g/dL or higher, without any of the organ damage that defines active myeloma.¹ Below 10 percent plasma cells with a lower M-protein, the condition is classified as MGUS, a precursor state that progresses at only about 1 percent per year. Above 60 percent plasma cells, the disease is reclassified as active myeloma regardless of symptoms, under updated diagnostic criteria.²

The key distinction is the absence of what clinicians call a “myeloma-defining event,” meaning no bone lesions, no kidney failure from the abnormal protein, no dangerously high calcium, and no severe anemia caused by the disease. A person with smoldering myeloma typically feels fine. The condition is usually discovered incidentally through blood work, which is part of what makes the treatment decision so psychologically complicated: you feel healthy, but your lab values say something abnormal is happening.

Why Risk Stratification Matters More Than the Diagnosis Itself

Not all smoldering myeloma behaves the same way. Some people remain stable for a decade or longer. Others progress to active myeloma within two years. The entire treatment conversation hinges on figuring out which group you fall into, because treating someone whose disease would never progress means exposing them to side effects and costs for no benefit.

The most widely used risk model is the Mayo Clinic’s “20/20/20” system, which flags three features: bone marrow plasma cells of 20 percent or more, serum M-protein of 2 g/dL or more, and a free light chain ratio of 20 or higher. Having none of those factors puts you in a low-risk category; having two or more makes you high-risk. In a validation study, each of those three markers individually carried a roughly three- to four-fold increased risk of progression.³ The high-risk group in that study had a median time to progression of just over two years, while the low- and intermediate-risk groups had not yet reached median progression at follow-up.

A more refined model from the International Myeloma Working Group (IMWG) adds chromosomal abnormalities detected by specialized testing into the scoring and separates patients into four tiers rather than three. The two-year risk of progression ranges from about 6 percent for low-risk patients all the way up to 63 percent for the highest-risk group when cytogenetic abnormalities are included.⁴ That spread is enormous, and it explains why blanket recommendations for or against treatment miss the point. The question is not “should smoldering myeloma be treated?” but “which smoldering myeloma patients benefit from treatment?”

Risk scores can also shift over time. A study evaluating serial application of these models found that patients could be reclassified as their disease markers evolved, which means a single assessment at diagnosis does not always capture the full picture.⁵ Repeat testing matters, even for those initially classified as low-risk.

The Evidence for Early Treatment

The debate over whether to treat smoldering myeloma or simply monitor it has been running for years, but the data have tilted decisively toward treatment for high-risk patients. A systematic review and meta-analysis pooling results from randomized controlled trials found that patients receiving anti-myeloma treatment had a 60 percent lower risk of disease progression or death compared to those who were only observed.⁶ That is a substantial effect, and it held across multiple trial designs.

The landmark Spanish trial published in the New England Journal of Medicine tested lenalidomide plus dexamethasone against observation in high-risk smoldering myeloma. After about three years of follow-up, the treatment group had not yet reached median time to progression, while the observation group progressed at a median of 21 months. Perhaps more striking, three-year survival was 94 percent with treatment versus 80 percent without it.⁷ This was one of the first trials to show not just delayed progression but an actual survival advantage.

A subsequent U.S. trial (E3A06) tested lenalidomide alone, without dexamethasone, against observation. Three-year progression-free survival was 91 percent with lenalidomide versus 66 percent with observation.⁸ The benefit was clear, though this trial enrolled a broader group of patients, not only those at the highest risk. Taken together, these two trials built a strong case that lenalidomide-based regimens delay or prevent progression to active myeloma in many patients.

Daratumumab and the First Approved Therapy

The most significant recent development is the AQUILA trial, which tested daratumumab, a monoclonal antibody that targets the CD38 protein on myeloma cells, against active monitoring in high-risk smoldering myeloma. With over five years of follow-up, daratumumab cut the risk of progression or death by 51 percent. Five-year progression-free survival was about 63 percent with daratumumab versus 41 percent with monitoring alone.⁹ There was also a trend toward improved overall survival, though longer follow-up is needed to confirm that fully.

This trial led to daratumumab becoming the first therapy approved specifically for high-risk smoldering myeloma, a milestone that fundamentally changed the treatment landscape.¹⁰ Before AQUILA, all treatment for smoldering myeloma was off-label or investigational. Now there is a formally approved option, which matters for insurance coverage, guideline recommendations, and the broader acceptance of early intervention as a valid strategy.

Daratumumab’s side-effect profile is generally more favorable than combination chemotherapy regimens. It is given as a subcutaneous injection, and the most common adverse effects are infusion-related reactions and upper respiratory infections. For patients and doctors who were hesitant about the toxicity of lenalidomide-based therapy in an otherwise asymptomatic person, daratumumab offers a different risk-benefit calculation.

What About More Aggressive Treatment Approaches

Some ongoing trials are testing whether the intensive combination regimens used for active myeloma could potentially cure or deeply suppress smoldering disease when given early. The logic is straightforward: if catching the disease before it causes organ damage gives you a smaller, less evolved tumor to fight, maybe you can eliminate it entirely rather than just delay its growth.

A review of the field notes that highly active treatments for active myeloma are now being investigated in the smoldering setting, with the aim of not just delaying but potentially preventing progression altogether.¹¹ This includes multi-drug combinations and even novel immunotherapies. The tension, though, is real: active myeloma remains incurable even with aggressive treatment, so it is not yet clear that throwing everything at smoldering disease early will change the ultimate outcome, or whether it simply pulls forward the toxicity of treatment that patients would eventually receive anyway.

Early data on bispecific antibodies and CAR-T cell therapy in smoldering myeloma are particularly intriguing. The Immuno-PRISM trial tested teclistamab, a bispecific antibody, in high-risk smoldering patients and reported a 100 percent overall response rate with deep remissions in 42 percent of patients at six months. A separate study of cilta-cel, a CAR-T therapy, reported complete remission and undetectable residual disease in all patients in the initial safety cohort.¹² These are very small, very early results, and whether such deep responses translate into long-term disease control or cure remains unknown. But they signal the direction the field is heading.

The Role of Imaging in Management Decisions

Imaging plays a surprisingly important role in smoldering myeloma, and not just as a diagnostic formality. The presence of bone lesions that are not visible on standard X-ray but show up on MRI or PET/CT can actually reclassify a patient from smoldering to active myeloma, triggering immediate treatment. Two or more focal lesions on MRI have been established as a myeloma-defining event, meaning they alone are sufficient reason to start therapy.¹³

Current guidelines recommend whole-body CT as the initial imaging technique when smoldering myeloma is suspected, followed by whole-body MRI if the CT is negative or inconclusive. For high-risk patients specifically, MRI appears to have a superior ability to detect diffuse and small-nodular patterns of bone marrow involvement that PET/CT can miss. In one prospective study, MRI led to a change in treatment approach for about 10 percent of high-risk smoldering myeloma patients by detecting findings that PET/CT did not.¹⁴ Getting the right scan matters because it directly influences whether you are told to watch and wait or to start treatment.

Measuring Treatment Success Without Symptoms

One of the unique challenges in treating smoldering myeloma is defining what success looks like. In active myeloma, you measure improvement by watching symptoms resolve, bone lesions stabilize, and organ function recover. In smoldering myeloma, there are no symptoms to track. Response is measured entirely through laboratory markers, such as the decline in M-protein or plasma cell percentage, and increasingly through minimal residual disease (MRD) testing, which looks for tiny amounts of remaining cancer cells.

Newer approaches are exploring blood-based MRD testing using cell-free DNA. One study using whole-genome sequencing of circulating DNA in high-risk smoldering myeloma found that this technique was concordant with traditional bone marrow-based MRD testing in about 73 percent of samples, and it picked up disease that bone marrow testing missed in some cases.¹⁵ Patients with higher levels of tumor DNA in their blood at baseline were more likely to have high-risk genetic features and to eventually progress. If validated in larger studies, blood-based MRD testing could reduce the need for repeat bone marrow biopsies, which are painful and inconvenient, particularly for patients who may be monitored for years.

The Cost and Quality-of-Life Equation

Treatment decisions in smoldering myeloma do not happen in a vacuum. The financial burden is considerable. In the United States, lenalidomide alone can cost over $17,000 per month, and more intensive multi-drug regimens used in active myeloma can run between $300,000 and $500,000 per year.¹⁶ For an asymptomatic condition where some patients might never progress, that financial exposure is a legitimate factor in the decision. Treatment algorithms that recommend lenalidomide-based therapy for two years in high-risk patients mean a significant cumulative cost, and the newer immunotherapies being studied are unlikely to be cheaper.

Quality of life is equally complex. Both the AQUILA trial (daratumumab) and the E3A06 trial (lenalidomide) reported improvements in health-related quality of life for treated patients, but the benefits appeared to be specific to the treatment used rather than universal.¹⁷ This makes sense when you consider that different drugs have different side-effect profiles. Lenalidomide causes fatigue, rash, and blood count changes in many patients. Daratumumab has fewer systemic side effects but requires regular clinic visits for injections. The “right” treatment depends partly on which trade-offs a given patient finds most tolerable.

There is also a psychological dimension that is easy to underestimate. Telling an asymptomatic person they need cancer treatment can fundamentally alter how they see themselves, creating anxiety, depression, and a sense of being “sick” that did not exist before the label was applied. Caregivers experience this too.¹² On the other hand, some patients find observation equally distressing because they feel like a ticking time bomb. There is no universally “better” option from a psychological standpoint; it depends on the individual.

Racial Disparities in Smoldering Myeloma

Myeloma, including its precursor stages, is two to three times more common in Black Americans than in white Americans. This disparity has long been recognized, but a more surprising finding has emerged from recent research: despite the higher incidence, Black patients with smoldering myeloma may actually have a lower risk of progression to active disease compared to white patients.¹⁸

A large analysis using the SEER database confirmed this pattern and added important detail. After adjusting for other factors, Black patients had significantly better cause-specific survival than white patients, with about a 31 percent lower risk of dying from the disease. American Indian and Alaska Native patients, by contrast, had the worst outcomes. Survival also varied significantly by income and socioeconomic status, suggesting that access to care compounds the biological differences.¹⁹ These findings matter clinically because risk models were largely developed and validated in predominantly white patient populations. Applying them uniformly across racial groups may overestimate the risk for Black patients and underestimate it for others.

The Immune Microenvironment and Why Some Cases Progress

Beyond the standard lab values used for risk scoring, researchers are increasingly interested in the immune environment surrounding the tumor cells. The path from MGUS to smoldering myeloma to active myeloma is not a single predictable escalator. Immune profiling studies have shown that the bone marrow microenvironment varies substantially between patients, and there appear to be multiple distinct pathways through which the immune system either contains or fails to contain the abnormal plasma cells.²⁰

This is relevant to treatment strategy because different immune environments might respond to different interventions. A patient whose immune system is already actively suppressing the tumor might benefit most from an immune-stimulating approach, while a patient whose immune defenses have already collapsed around the tumor might need direct cell-killing therapy. None of this is yet part of routine clinical decision-making, but it hints at a future where treatment for smoldering myeloma is tailored not just by how much disease is present but by what the immune system is doing about it.

Diet, Weight, and Lifestyle Factors

Given that smoldering myeloma can linger for years before progressing (if it progresses at all), patients naturally ask whether anything they do in daily life can shift the odds. The honest answer is that the evidence is early-stage but not dismissive. Obesity and metabolic dysfunction have been linked to worse outcomes in plasma cell disorders, and pilot studies are exploring whether dietary interventions can modify disease-relevant biology.

The NUTRIVENTION study tested a high-fiber, plant-based dietary intervention in overweight and obese patients with MGUS and smoldering myeloma.²¹ Updated results showed the diet was safe, feasible, and improved metabolic markers including insulin resistance, gut microbiome diversity, and inflammatory profiles.²² Whether these biological improvements actually translate into delayed progression to myeloma will require larger and longer studies. But for patients looking for something actionable beyond medication or monitoring, maintaining a healthy weight and eating a fiber-rich diet appears to be a reasonable and low-risk strategy that aligns with the emerging biology.

How Treatment Decisions Are Made in Practice

The European Myeloma Network’s consensus position captures the current real-world situation well: outside of clinical trials, the conventional approach to smoldering myeloma generally remains observation until progression, but the evidence from recent trials has made early treatment a validated option for higher-risk patients.²³ In practice, current treatment algorithms suggest that high-risk patients should be offered lenalidomide-based therapy for about two years or enrolled in clinical trials, while low-risk patients should be monitored every three to four months without treatment.²⁴

With daratumumab now approved, the menu of options for high-risk patients has expanded. The choice between lenalidomide-based treatment and daratumumab typically depends on patient factors: age, other health conditions, tolerance for side effects, distance from a treatment center, and personal preferences about the type and duration of therapy. Clinical trial enrollment remains strongly encouraged, especially for patients with intermediate-risk disease where the benefit of treatment is less well established. For truly low-risk smoldering myeloma, where the two-year progression risk is in the single digits, the math still favors observation. Treating these patients would mean many receive therapy they never needed, since their disease might have remained stable for years or even decades.

The conversation between doctor and patient is unusually important in this setting. Unlike many cancers where the urgency of treatment is obvious, smoldering myeloma leaves room for genuine disagreement about the best path forward. A patient who finds the uncertainty of monitoring intolerable may reasonably choose treatment even if their risk score is borderline. Another patient with the same risk score who dreads side effects and clinic visits may reasonably prefer monitoring with the understanding that treatment will begin promptly if the disease evolves. Neither choice is wrong; the evidence supports both approaches for a substantial portion of patients who fall in the gray zone between clearly low- and clearly high-risk.