Staging and Risk Stratification
When multiple myeloma is diagnosed, the stage of the disease varies from patient to patient. The most commonly used clinical staging system, the Durie-Salmon Staging System, demonstrates the correlation between the amount of myeloma and the damage it has caused, such as bone disease or anemia.
Staging a can also be done according to prognosis, or expected survival. The most common staging system for MM that is based on prognostic factors is the Revised International Staging System (R-ISS).
Multiple Myeloma Prognosis
A multiple myeloma prognosis is determined by both the number and specific properties of myeloma cells in a given patient. These specific properties include the following:
- the growth rate of myeloma cells,
- the production rate of monoclonal proteins, and
- the production or non-production of various cytokines and chemicals that damage or significantly impair other tissues, organs, or bodily functions.
Durie-Salmon Staging System
In 1975, the Durie-Salmon Staging System was developed, bringing together the major clinical parameters in correlation with measured myeloma cell mass (the total number of myeloma cells in the body).
International Staging System (ISS)
In 2005, a new staging system was developed by the IMF's research division, the International Myeloma Working Group (IMWG). Clinical and laboratory data were gathered on 10,750 previously untreated symptomatic MM patients from 17 institutions, including sites in North America, Europe, and Asia. Potential prognostic factors were evaluated using a variety of statistical techniques. Serum β2 microglobulin (Sβ2M), serum albumin, platelet count, serum creatinine, and age emerged as powerful predictors of survival and were then further analyzed.
A combination of serum β2 microglobulin and serum albumin provided the most powerful, simple, and reproducible three-stage classification. This system, the International Staging System, was further validated by demonstrating effectiveness
- in patients in North America, Europe, and Asia;
- in patients younger and older than age 65 years;
- with standard therapy or auto transplant; and
- in comparison with the Durie-Salmon Staging System.
Revised International Staging System (R-ISS)
In August 2015, the IMWG published the Revised International Staging System (R-ISS) for multiple myeloma to incorporate two further prognostic factors: genetic risk as assessed by fluorescence in-situ hybridization (FISH), and level of lactate dehydrogenase level (LDH).