Plasma cell dyscrasias are a group of related disorders which include; Multiple Myeloma (multiple forms), Waldenström’s macroglobulinemia, Heavy and Light chain disease, and other Immunoglobulin secreting neoplasms. Generally, these all involve the expansion of a single clone of an Immunoglobulin secreting cell (end stage B cell to plasma cell). While this Webinar will focus primarily on important laboratory issues when developing clinical trials involving Multiple Myeloma, many of the issues to be discussed are also relevant to the other plasma cell dyscrasias. Multiple myeloma accounts for approximately 15% of all hematopoietic malignancies and has a bleak prognosis. To address this, there is considerable effort to develop new treatments for this not uncommon malignancy. Paramount to the correct assessment of the efficacy of these new treatment trials is accurate laboratory monitoring.
In Multiple Myeloma, it is the abnormal plasma cells, their products (immunogloublins; IgG, IgM, IgA, IgD, and IgE classes), and their effect on the body chemistries, which is the basis for laboratory diagnosis and monitoring of this disease. Specifically, quantitation of the monoclonal proteins secreted by the malignant plasma cells in the serum and urine are primary routine monitoring tools. In fact, the International Response Criteria (IRC) uses the quantification of the monoclonal proteins in the serum and urine using serum electrophoresis and Immunofixation testing to assess degrees of response to treatment in addition to a determination of the number of plasma cells found in the bone marrow. In addition, the monoclonal proteins are also often monitored by examining total immunoglobulin levels (usually only IgG, IgM, and IgA, as IgE and IgD myelomas are very rare). While these are very accurate when the tumor burden is high, they can become very inaccurate when the tumor burden is low. There are now new technologies available which can more accurately assess monoclonal antibodies via IgG, IgM, and IgA quantitation by further quantifying the immunoglobulins by their light chain as well (ex. IgG kappa and IgG lambda).
In assessing the involvement and response to treatment by serum electrophoresis and Immunofixation, variability in testing must be kept to a minimum. Both of these tests have degrees of subjectivity to the method which is highly dependent on the skills and experience of the technologists and the laboratory performing the test. In fact, a 2015 College of American Pathologists (CAP) proficiency survey demonstrated that between different manufacturers’ methods and across laboratories, a variation of 221% in the quantitation of the monoclonal protein in serum electrophoresis was found. When one compared different laboratories using the same method, this variation dropped, but still averaged 150%. In addition, the interpretation of serum electrophoresis and Immunofixation testing in Multiple Myeloma trials has been further complicated by many of the treatments themselves. In trials utilizing targeted therapeutic monoclonal antibodies, the drug itself has been reported to interfere with proper assessment of the patient. The ability to identify and recognize this is critical to proper interpretation and assessment of the therapeutic response, so that bone marrow evaluations can be performed at appropriate times to confirm the response. This underscores the importance of following myeloma patients in a laboratory with a dedicated group of myeloma experienced technologists. This is even more important in clinical trials as there are steps which a centralized myeloma experienced clinical trials laboratory can take to keep this variation to a minimum and insure accurate assessment of trial subjects.