OBJECTIVES: Data on the diagnosis and treatment of smoldering multiple myeloma (SMM) by risk level for progression to active MM are needed to clarify burden of illness and unmet patient needs. Real-world SMM burden of illness is not well-understood, as retrospective databases do not capture these data. We conducted a Delphi panel study to assess expert consensus on diagnosis, risk-stratification, treatment practices and their impact in high-risk SMM.

METHODS: Experts (24 from 5 countries) in MM and SMM participated on a Delphi panel. Round 1 surveyed SMM diagnosis, risk stratification, and treatment approach. In round 2, panelists verified their responses after reviewing country-level summary responses. In round 3, consensus (defined as strong agreement by experts [≥75%]) statements were rated based on survey outputs.

RESULTS: Experts strongly agreed (92%) that risk stratification is integral to initial SMM diagnosis. Most panelists used IMWG 2020 and Mayo 2018 risk models, with variable use of PETHEMA 2007. Consensus was mostly reached that ~20% (mean estimates range 22%-36%) of newly diagnosed SMM patients have high-risk SMM per these criteria. While no standardized risk stratification approach was apparent from panel responses, the consensus was to use IMWG 2020, except France, where Mayo 2018 was preferred. Experts (79%) indicated they treat high-risk SMM patients (mostly within clinical trials). Consensus, except for France, was that fewer patients with high-risk SMM progress to MM over 1-year of being treated (mean estimates, 8.3% [standard error of mean (SEM), 3.0%]) versus not (35.9% [4.7%]). Experts agreed (71%) that high-risk SMM patients have slower progression to MM when treated versus not (median estimated time to progression 40 versus 24 mo, respectively).

CONCLUSIONS: These results highlight the need for standardized risk stratification of SMM. Additionally, these findings support that high-risk treatment may lead to better outcomes and the need for an approved treatment.