‘High Prevalence’ of Smoldering Myeloma Observed in Nationwide Screening Study

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A nationwide screening study suggests the prevalence of smoldering multiple myeloma (SMM) is 0.5% among individuals age 40 or older, and more than one-third of patients have intermediate- or high-risk SMM.

These results, from the iStopMM study, were presented at the 2021 American Society of Hematology (ASH) Annual Meeting by Sigrün Thorsteinsdottir, MD, PhD, of the University of Iceland in Reykjavik.

For this study, all residents of Iceland age 40 or older were invited to participate and undergo serum protein electrophoresis (SPEP) and free light chain (FLC) testing.


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Patients with abnormal screening results (M protein ≥ 3g/dL; FLC ratio ≥ 100) were randomly assigned to 1 of 3 arms. Patients in arm 1 had no further work-up. Patients in arm 2 were managed according to current guidelines. Patients in arm 3 underwent intensive follow-up with bone marrow testing and whole-body low-dose CT.

Patients were diagnosed with SMM if they had bone marrow plasma cell infiltration of 10% to 60% and/or serum M protein concentration of at least 3g/dL, in the absence of myeloma-defining events.

Results

A total of 75,422 individuals were screened, and 3725 were included in the randomization due to an abnormal screening result.

There were 1503 patients who underwent bone marrow biopsy, and 180 were diagnosed with SMM. These patients had a median age of 70 years (range, 44-92 years), and 61% were men.

M protein was present in 84% of patients — with a median concentration of 0.5 g/dL (range, 0.01-3.5 g/dL) — and 14% of patients had abnormal FLC results only. The FLC ratio was abnormal in 64% of patients.

Of the 1279 patients assigned to arm 3, bone marrow sampling was done in 970 patients, and 105 of them — 10.8% — were diagnosed with SMM.

Using this result, the researchers estimated the prevalence of SMM to be 0.53% among individuals age 40 or older. When stratified by sex, the prevalence was 0.70% in men and 0.37% in women. Prevalence increased with age.

The researchers then stratified SMM patients using 2 models.

Using the Mayo 2018 model — applied to all 180 SMM patients identified — 64% were considered at low risk of progressing to MM, 26% at intermediate risk, and 10% at high risk.

Using the Spanish Myeloma Group model — applied to 73 patients with flow cytometry results — 53% were at low risk, 29% at intermediate risk, and 18% at high risk.

“These results underline the necessity for improved risk stratification in smoldering myeloma,” Dr Thorsteinsdottir said. “The high prevalence of smoldering myeloma has implications for future treatment policies because … treatment initiation at the smoldering stage is likely to be included in guidelines soon.”

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.

Read more of Cancer Therapy Advisor’s coverage of the ASH 2021 meeting by visiting the conference page.

Reference

Thorsteinsdottir S, Gislason GK, Aspelund T, et al. Prevalence of smoldering multiple myeloma: Results from the Iceland Screens, Treats, or Prevents Multiple Myeloma (iStopMM) study. Presented at ASH 2021; December 11-14, 2021. Abstract 151.



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