International Staging System (ISS) for multiple myeloma
Three-stage prognostic staging from serum β2-microglobulin and albumin.
Switch how results are explained
ISS stage I: β2-microglobulin < 3.5 mg/L and albumin ≥ 3.5 g/dL. Median survival was 62 months in the original cohort.
- Evidence grade
- A
What it is and when to use it
The ISS combines two routine serum tests measured at diagnosis: β2-microglobulin (mg/L) and albumin (g/dL). Stage I: β2-microglobulin < 3.5 mg/L and albumin ≥ 3.5 g/dL. Stage III: β2-microglobulin ≥ 5.5 mg/L, whatever the albumin. Stage II: everything else.
How to interpret it
In the 2005 derivation cohort of more than ten thousand patients, median survival was 62 months in stage I, 44 months in stage II and 29 months in stage III. Survival is longer with current treatments, but the stages still separate risk.
Limitations and when not to use it
Applies to symptomatic multiple myeloma at diagnosis, not to MGUS or smouldering myeloma. β2-microglobulin rises with renal impairment, so stage III may partly reflect kidney function. Enter albumin in g/dL: divide g/L by 10. The R-ISS refines this staging with cytogenetics and LDH.
Formulas and cut-offs are from the original authors of each score; see the references.
Last reviewed: June 2026
References
- Greipp PR, San Miguel J, Durie BGM, et al. International staging system for multiple myeloma. J Clin Oncol. 2005;23(15):3412-3420. PMID:15809451