The serum free light chain assay can be used to detect disease progression in Intact Immunoglobulin Multiple Myeloma patients who at relapse switch to production of light chains only.

For some Intact Immunoglobulin Multiple Myeloma (IIMM) patients in remission, relapse is accompanied by a marked rise in monoclonal serum free light chains (FLC) with no associated increase in intact immunoglobulin concentrations. This phenomenon is known as light chain (LC) escape or Bence-Jones escape.¹

A model of light chain escape in a hypothetical patient with IIMM. Dual plasma cell subsets are present at diagnosis producing either monoclonal intact immunoglobulin and FLC or FLC alone. In response to chemotherapy, intact immunoglobulin and serum FLC concentrations fall (FLC fall more rapidly due to their shorter half life). Disease relapse with light chain escape is associated with proliferation of the light chain only plasma cell clone but not the intact immunoglobulin producing clone. This leads to a marked rise in serum FLC but no associated change in the intact immunoglobulin concentration.

Why is it important to detect light chain escape early?

• Light chain escape is associated with increased tumor growth and is indicative of disease progression.²
• Early detection of light chain escape may avoid unnecessary complications such as renal impairment.²

Progressive increases in the clonal free light chain accompanied by progressive abnormalities in the free light chain ratio is often a reliable measurement of disease progression and ilght chain escape may be detected when monitoring with Freelite®.^2-3