2
44
months
45
%
0
0
2
44
months
45
%
0
0
The International Staging System (ISS) for multiple myeloma is a simple yet powerful prognostic tool based on just two laboratory measurements: serum beta-2 microglobulin and serum albumin. Published in 2005 by Greipp and colleagues in the Journal of Clinical Oncology, the ISS was derived from analysis of over 10,000 patients across 17 institutions worldwide.
Multiple myeloma is a malignancy of plasma cells that accounts for approximately 10% of all hematologic malignancies, with roughly 35,000 new cases per year in the United States. Despite significant treatment advances including proteasome inhibitors, immunomodulatory drugs, and monoclonal antibodies, myeloma remains incurable in the vast majority of patients. Accurate staging is essential for prognostication and treatment planning.
The ISS's strength lies in its remarkable simplicity. It requires only two readily available and inexpensive laboratory tests. Serum beta-2 microglobulin (B2M) is a protein shed by myeloma cells that reflects tumor burden and renal function — two critical prognostic factors. Serum albumin reflects the patient's overall nutritional status and inversely correlates with IL-6 levels, a key myeloma growth factor.
The ISS defines three stages: Stage I (B2M <3.5 mg/L AND albumin >=3.5 g/dL, median survival 62 months), Stage II (neither Stage I nor III), and Stage III (B2M >=5.5 mg/L, median survival 29 months). This simple stratification provides excellent discrimination of survival outcomes and has been validated worldwide.
While the ISS has been supplemented by the Revised ISS (R-ISS) which adds cytogenetic risk and LDH, the original ISS remains widely used due to its simplicity and applicability in settings where FISH and LDH may not be readily available. It is also used as a stratification factor in virtually all myeloma clinical trials.
The ISS has been endorsed by the International Myeloma Working Group (IMWG) and is included in all major myeloma treatment guidelines including NCCN, ESMO, and BSH. It provides a universal language for discussing myeloma prognosis across different healthcare settings and geographic regions.
The ISS uses two laboratory values to define three stages:
Median survival: Stage I ~62 months, Stage II ~44 months, Stage III ~29 months.
ISS Stage I: Favorable prognosis, median survival ~62 months, ~66% 5-year OS. Low tumor burden and good nutritional status. Stage II: Intermediate prognosis, ~44 months median, ~45% 5-year OS. Stage III: Higher tumor burden, ~29 months median, ~33% 5-year OS. Note: these survival estimates are from the pre-novel-agent era; current outcomes with modern treatment are significantly better.
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Results
Low B2M and normal albumin. ISS Stage I with favorable prognosis. Median survival 62 months.
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Results
Elevated B2M >= 5.5. ISS Stage III. Median survival 29 months. Consider aggressive treatment approach.
The ISS (International Staging System) is a simple prognostic tool for multiple myeloma using two blood tests: serum beta-2 microglobulin and serum albumin. It classifies patients into three stages with distinct survival outcomes.
Beta-2 microglobulin is a protein found on the surface of most nucleated cells. In myeloma, elevated levels reflect higher tumor burden. It is also affected by renal function, as it is cleared by the kidneys.
Low serum albumin in myeloma correlates with higher IL-6 levels (a key myeloma growth factor), poor nutritional status, and increased inflammatory burden. It is an independent adverse prognostic factor.
R-ISS adds cytogenetic risk (high-risk: del(17p), t(4;14), t(14;16)) and LDH to ISS. R-ISS provides better discrimination, particularly identifying the highest-risk subgroup. ISS remains useful when FISH is unavailable.
The original ISS survival estimates are from the pre-novel-agent era. With modern treatments (proteasome inhibitors, IMiDs, anti-CD38 antibodies), all ISS stages have significantly better outcomes, but relative differences between stages persist.
The ISS is typically assessed at diagnosis for prognostication and clinical trial stratification. While B2M and albumin change with treatment, ISS stage is not routinely reassessed — response assessment uses different criteria.
Durie-Salmon was the previous myeloma staging system using hemoglobin, calcium, M-protein level, and skeletal lesions. It has been largely replaced by ISS and R-ISS due to subjectivity in skeletal assessment and inferior prognostic discrimination.
ISS was developed for symptomatic (active) myeloma requiring treatment. It is not validated for smoldering myeloma, which has its own risk stratification models based on M-protein level, free light chain ratio, and bone marrow plasma cell percentage.
Stage III patients typically receive aggressive multi-drug regimens (e.g., VRd: bortezomib, lenalidomide, dexamethasone) followed by autologous stem cell transplant in eligible patients. Anti-CD38 antibodies may be added for high-risk disease.
Minimal residual disease (MRD) assessment by flow cytometry or next-generation sequencing is emerging as a powerful prognostic tool that may supplement or refine ISS staging. MRD-negative patients have significantly better outcomes across all ISS stages.
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