There are precursors to active multiple myeloma; the earliest is called monoclonal gammopathy of undetermined significance (MGUS). It is characterized by an excess of M-proteins in the blood, however it is benign and asymptomatic. MGUS occurs in 3–4 % of people over the age of 50, although only 1% of patients with MGUS will advance to active multiple myeloma each year.
Smoldering multiple myeloma (SMM) is an intermediate step between MGUS and active multiple myeloma. SMM is diagnosed when patients have an excess of M-protein in the blood and elevated level of plasma cells in their bone marrow. SMM is also asymptomatic. There are approximately 250,000 people with SMM in the US and 10 – 15 % will advance to active multiple myeloma within 5 years.
There are currently no diagnostic or prognostic tests that accurately identify the high-risk SMM patients likely to transition to active multiple myeloma.
Industry is turning towards identifying patients in the high-risk category of SMM for earlier treatment to delay the onset of active multiple myeloma and its debilitating symptoms.