Study Tracks Progression from Smoldering to Active Multiple Myeloma

Study Tracks Progression from Smoldering to Active Multiple Myeloma

According to the results of a study published in the New England Journal of Medicine, the risk of progressing from smoldering (asymptomatic) to active multiple myeloma varies by initial levels of bone marrow plasma cells and serum monoclonal protein.

Multiple myeloma is a cancer of the blood that affects the plasma cells. Plasma cells are an important part of the immune system; they produce antibodies to help fight infection and disease. Multiple myeloma is characterized by an excess production of abnormal plasma cells. Symptoms include increased risk of bacterial infections and impaired immune responses.

Smoldering multiple myeloma refers to asymptomatic multiple myeloma (multiple myeloma without symptoms). Patients with smoldering multiple myeloma have a high risk of eventually progressing to symptomatic (active) multiple myeloma.

To describe the clinical course and prognosis of patients with smoldering multiple myeloma, researchers at the Mayo Clinic evaluated the medical records of patients who had been diagnosed between 1970 and 1995.

Of 3,549 patients diagnosed with multiple myeloma, 276 (8%) met the criteria for smoldering multiple myeloma. These criteria included a serum monoclonal protein level of 3 grams per deciliter or more and/or a proportion of plasma cells in the bone marrow of 10% or more, and no end-organ damage. End-organ damage that can result from plasma-cell proliferation includes high calcium levels, kidney problems, anemia, bone changes, and repeated bacterial infections.

  • Overall, the probability of progressing to active multiple myeloma or amyloidosis was 51% after five years, 66% after 10 years, and 73% after 15 years.
  • The risk of progressing to active multiple myeloma or amyloidosis varied by the initial level of plasma cells in the bone marrow and monoclonal protein in the serum:
    • Among patients with a high proportion of bone marrow plasma cells (10% or higher) and high serum monoclonal protein (3 grams per deciliter or higher), the 15-year risk of developing active multiple myeloma or amyloidosis was 87%.
    • Among patients with a high proportion of bone marrow plasma cells (10% or higher) and lower serum monoclonal protein (less than 3 grams per deciliter), the 15-year risk of developing active multiple myeloma or amyloidosis was 70%.
    • Among patients with a low proportion of bone marrow plasma cells (less than 10%) and high serum monoclonal protein (3 grams per deciliter or higher), the 15-year risk of developing active multiple myeloma or amyloidosis was 39%.

The researchers conclude that the risk of progressing from smoldering to active multiple myeloma varies with the proportion of bone marrow plasma cells and the serum monoclonal protein level at diagnosis.

Reference: Kyle RA, Remstein ED, Therneau EM et al. Clinical course and prognosis of smoldering (asymptomatic) multiple myeloma. New England Journal of Medicine. 2007;356:2582-90.

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