What Is B2m in Multiple Myeloma?

Multiple myeloma is a cancer of the plasma cells, white blood cells in the bone marrow. Abnormal plasma cells multiply in multiple myeloma, which in turn raises the number of plasma cells. Because these cells make proteins, typically protein levels in the blood go up in multiple myeloma as well.

Identification

• Beta 2 microglobulin, or B2m, is a protein produced by myeloma cells. Its presence is helpful in both the diagnosis and staging of multiple myeloma.

Staging System

• The International Myeloma Working Group, IMWG, sets the standards for staging the disease based on levels of B2m and albumin in the blood. Stage 1 is B2m below 3.5, with a median survival at 62 months; stage 2 is B2m between 3.5 and 5.5 with a median survival at 44 months; stage 3 is B2m over 5.5 with a median survival at 29 months.

Procedure

• To check levels of B2m, typically a blood sample is drawn from a vein in the arm. Sometimes urine or cerebrospinal fluid is checked. The levels are useful in diagnosing, staging and monitoring treatment of multiple myeloma.

Function

• B2m levels are tumor markers. These are substances, most often proteins, that are produced by the body in response to cancer growth and indicative of the tumor burden or amount of cancer present. B2m levels can not determine whether a patient has multiple myeloma, as increased levels are associated with other ailments as well, such as kidney disease.

Significance

• When B2m levels are checked during treatment, decreasing numbers indicate a good response, while stable or increasing levels mean the person is not responding to treatment.