Multiple Myeloma International Staging System (ISS)
Why Use
Multiple myeloma (MM) is a heterogeneous disease, with prognosis affected by various patient and disease related factors (ISS stage, genetics, performance status and other comorbidities). The ISS differentiates patients into 3 separate prognostic groups. The staging is prognostic but does not necessarily guide treatment decisions in the upfront setting. It provides survival information to the physician and patient, and helps stratify patients in current clinical trials. Preferred over the Durie-Salmon system for its simplicity and objectivity, primarily in assessment of bony disease.
When to Use
Newly diagnosed MM patients. Its utility has not been validated in relapsed myeloma, smoldering myeloma or MGUS patients.
Formula
Pearls / Pitfalls
The International Staging System (ISS) for multiple myeloma defines 3 subgroups with differing overall survival: Stage I- 62 months Stage II- 44 months Stage III- 29 months The ISS was developed as a simpler, more objective tool to provide prognostic information for newly diagnosed, symptomatic MM patients. It does not reflect disease burden. Durie-Salmon, a cumbersome staging system used in the past, was based on estimating the disease burden but ultimately did not prove to be prognostic and fell out of favor. Compared to older staging systems, ISS is a simple prognostic tool and may be used to stratify patients on MM clinical trials.
Advice
Many MM patients are treated through clinical trials. Physicians may consider referring patients to academic treatment centers if they are eligible and willing to receive transplantation, not only to discuss standard treatment options, but also to consider clinical trial options.
More Information
Multiple Myeloma ISS interpretation: Stage Criteria I Serum β2 microglobulin <3.5 mg/L AND serum albumin ≥ 3.5 g/dL II Either: serum β2 microglobulin <3.5 mg/L, but serum albumin <3.5 g/dL OR serum β2 microglobulin 3.5 – 5.4 mg/L irrespective of the serum albumin III Serum β2 microglobulin ≥5.5 mg/L