The Revised International Staging System (R-ISS), the most widely used staging system for multiple myeloma (MM), is based on lactate dehydrogenase, albumin, high-risk genetic markers by FISH, and beta-2 microglobulin. However, it does not account for additional risk associated with multiple genetic abnormalities or the presence of Gain1q. As a result, the majority of patients are classified as R-ISS Stage 2, despite considerable heterogeneity. Recently, two new staging systems, the Mayo Additive Staging System (MASS) and the Second Revision of the International Staging System (R2-ISS), have been proposed. Both systems incorporated additional risk factors into the classification process. A comparison of the performance of these two systems has not been previously conducted.
In this study, researchers aimed to externally demonstrate the application of these staging systems and compare their performances in a large, contemporary cohort of patients in the United States.
Why this matters
This study represents the first comparison of the newer staging systems to each other, and the first to externally validate them in a large multi-center contemporary US cohort receiving modern triplet therapy. It reveals that the newer systems, MASS and R2-ISS, perform comparably to R-ISS in a contemporary MM patient cohort. A key advantage is their ability to reclassify previously R-ISS Stage II patients into more refined risk-stratified subsets. This finding advocates for greater use of these novel systems in routine clinical practice to enhance risk stratification for MM patient staging.