ISS Myeloma Staging Calculator
ISS Myeloma Staging Calculator
Stage newly diagnosed multiple myeloma from beta-2 microglobulin and albumin, and see how R-ISS builds on it.
ISS Myeloma Staging
β2M + albumin → stageβ2M 4.2 mg/L, albumin 3.1 g/dL
ISS staging criteria
Stage II: neither the Stage I nor the Stage III criteria
Stage III: β2M ≥ 5.5 mg/L
- β2M
- beta-2 microglobulin, mg/L — reflects both tumour burden and renal function
- albumin
- g/dL — divide a result given in g/L by 10
- R-ISS
- the Revised ISS adds LDH and high-risk cytogenetics (del17p, t(4;14), t(14;16)) and discriminates outcomes better; it is now the preferred system where those results are available
Worked example
β2M 4.2 mg/L, albumin 3.1 g/dL
β2M 4.2 is below 5.5 → not Stage III
β2M 4.2 is not below 3.5 → not Stage I
→ Stage II by exclusion
ISS survival by stage (original cohort)
| Stage | Criteria | Median OS (original series) |
|---|---|---|
| I | β2M < 3.5 mg/L and albumin ≥ 3.5 g/dL | 62 months |
| II | Neither Stage I nor Stage III | 44 months |
| III | β2M ≥ 5.5 mg/L | 29 months |
What the two values represent, and where R-ISS improves on this
The International Staging System stages newly diagnosed multiple myeloma using two values that are available almost everywhere: serum beta-2 microglobulin and serum albumin. In the original 2005 series, median overall survival was 62, 44 and 29 months for stages I, II and III respectively. Modern combination therapy, autologous transplantation and novel agents have extended survival substantially at every stage since, so these figures are best used to show relative separation between stages rather than quoted as a current prognosis.
Beta-2 microglobulin works as a staging marker because it reflects tumour burden — it is shed from the surface of malignant plasma cells in proportion to their number — but this is also its weakness, because it is cleared renally, and any cause of renal impairment raises it independently of disease burden. A patient with modest tumour burden but significant renal impairment can therefore be over-staged.
The Revised ISS adds lactate dehydrogenase and high-risk cytogenetics — del17p, t(4;14) and t(14;16) — to the same two values, and discriminates outcomes considerably better than ISS alone. It is now the preferred staging system where cytogenetic results are available, though the original ISS remains widely quoted and reported. Albumin must be entered in g/dL; a result reported in g/L should be divided by 10 first.
Frequently asked questions
What is the difference between ISS and R-ISS?
ISS uses only beta-2 microglobulin and albumin. R-ISS adds LDH and high-risk cytogenetics (del17p, t(4;14), t(14;16)) and separates outcomes better. R-ISS is now the preferred system when cytogenetics are available.
Why does renal impairment affect the ISS stage?
Beta-2 microglobulin is cleared by the kidney. Renal impairment from any cause raises it independently of tumour burden, which can push a patient with modest disease into a higher apparent stage.
What albumin unit does ISS use?
Grams per decilitre (g/dL). If your laboratory reports albumin in g/L, divide by 10 before entering it — using g/L directly gives a meaningless stage.
Are the original ISS survival figures still accurate?
No, not as absolute numbers. They come from a 2005 cohort treated before current combination therapy and transplantation became standard. The stages still separate risk meaningfully; the specific months should be read as relative, not current.
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References
- Greipp PR et al. International staging system for multiple myeloma. J Clin Oncol. 2005;23(15):3412–20.
- Palumbo A et al. Revised International Staging System for multiple myeloma: a report from International Myeloma Working Group. J Clin Oncol. 2015;33(26):2863–9.