The short answer
Myeloma staging does not describe where the cancer sits. CRAB - high calcium, renal problems, anemia, bone damage - decides whether smoldering myeloma has turned active. The R-ISS then uses beta-2-microglobulin, albumin, LDH and FISH chromosome results to place active disease in stage I, II or III.
CRAB stands for high calcium, renal problems, anemia and bone damage, and any one moves smoldering myeloma to active.
Myeloma staging combines blood test results rather than describing where the cancer sits in the body.
R-ISS stage III means beta-2-microglobulin at or above 5.5 mg/L plus high LDH or high-risk chromosome changes.
Stage is a snapshot used for planning and comparison, not a countdown clock for any one person.
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The full explanation.
Why staging comes after diagnosis
Once a bone marrow biopsy confirms multiple myeloma, two questions follow. How much disease is present? How is it likely to behave? Staging answers part of that question. It does not describe where the cancer is, the way staging does for a tumor like breast or lung cancer. Instead, it combines blood test results to estimate how much myeloma is in your body and how aggressive it may be.
The CRAB criteria: from "smoldering" to "active"
Doctors first decide whether myeloma is active enough to need treatment now. They look for four types of organ damage. Doctors remember them with the letters CRAB: high Calcium in the blood, Renal (kidney) problems, Anemia (low red blood cells), and Bone damage, such as fractures or lesions on imaging. Finding one or more of these moves someone from "smoldering myeloma" into "active myeloma." Certain high-risk lab markers can do the same, even without symptoms. Smoldering myeloma is watched. Active myeloma is treated.
The Revised International Staging System (R-ISS)
Active myeloma is staged using the R-ISS, which relies on three blood results plus chromosome testing:
- Stage I: Beta-2-microglobulin under 3.5 mg/L, albumin at or above 3.5 g/dL, no high-risk chromosome changes, and normal LDH (a blood enzyme).
- Stage II: Results that fall between stage I and stage III.
- Stage III: Beta-2-microglobulin at or above 5.5 mg/L, combined with either a high LDH level or specific high-risk chromosome changes found on FISH testing.
Beta-2-microglobulin is a protein made by myeloma cells; higher levels usually mean more disease. Albumin is a protein made by the liver; lower levels can reflect how sick the body is from the disease. Stage is a snapshot used for planning and comparing outcomes across large groups of patients. It is not a countdown clock for any one person.
What staging does and does not decide
A higher R-ISS stage generally means your team will consider more intensive treatment combinations. It also affects how outcomes are discussed and compared in research. It does not by itself rule any treatment in or out, and people at every stage are treated with the goal of controlling the disease, often for years. Your chromosome (cytogenetic) results, kidney function, age, and overall fitness all shape the plan alongside the stage number.
What happens after staging
Staging results feed into a first-treatment plan. This commonly combines a targeted drug, an immunotherapy-type drug called a monoclonal antibody, and a steroid. Many people who are fit enough are also considered for a stem cell transplant using their own cells, either soon after diagnosis or later. Ask your team to walk through why a specific combination and timing were chosen for your stage and risk category.
What to ask your team
- Do I meet CRAB criteria, or am I being watched as smoldering myeloma?
- What is my R-ISS stage, and which lab values determined it?
- Are my chromosome (cytogenetic) results standard-risk or high-risk?
- How does my stage affect the treatment being recommended?
- Is a stem cell transplant part of my plan, and if so, when?
When to get help sooner
- Call 911 or go to an emergency department if back pain comes with new weakness in your legs, numbness, or trouble controlling your bladder or bowel. Myeloma weakens the spine, and pressure on the spinal cord has to be relieved fast to protect walking.
- Call 911 or go to an emergency department if you become confused or very drowsy, with heavy thirst, vomiting and weak muscles. That mix points to the high calcium in the C of CRAB, which needs treatment in hospital. Do the same if your temperature reaches 100.4°F (38°C) or higher, since low antibody levels make infection dangerous here and CDC treats fever during cancer treatment as an emergency.
- Call your care team the same day if you are passing much less urine than usual, or your ankles and face are puffy. Myeloma can damage the kidneys, the R in CRAB.
- Call your care team within a day or two if a bone starts hurting sharply after a small knock, or tiredness and breathlessness are creeping up on you. These match the B and A of CRAB.
Sources
Words to know
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Common questions
Why does staging work differently in myeloma?
Once a bone marrow biopsy confirms multiple myeloma, staging does not describe where the cancer is, the way it does for a tumor like breast or lung cancer. Instead it combines blood test results to estimate how much myeloma is in your body and how aggressive it may be.
What are the CRAB criteria?
They are the four types of organ damage doctors look for when deciding whether myeloma is active enough to need treatment now: high Calcium in the blood, Renal (kidney) problems, Anemia, and Bone damage such as fractures or lesions on imaging. Finding one or more moves someone from smoldering myeloma into active myeloma, and certain high-risk lab markers can do the same even without symptoms. Smoldering myeloma is watched. Active myeloma is treated.
What is the R-ISS?
The Revised International Staging System, used for active myeloma. It relies on three blood results plus chromosome testing. Stage I is beta-2-microglobulin under 3.5 mg/L, albumin at or above 3.5 g/dL, no high-risk chromosome changes and normal LDH. Stage III is beta-2-microglobulin at or above 5.5 mg/L combined with either a high LDH level or specific high-risk chromosome changes found on FISH testing. Stage II is everything that falls in between.
Does my stage decide my treatment?
Not on its own. A higher R-ISS stage generally means your team will consider more intensive treatment combinations, and it affects how outcomes are discussed and compared in research. But it does not by itself rule any treatment in or out, and people at every stage are treated with the goal of controlling the disease, often for years. Your chromosome results, kidney function, age and overall fitness all shape the plan alongside the stage number.
What happens after staging?
Staging results feed into a first-treatment plan, which commonly combines a targeted drug, an immunotherapy-type drug called a monoclonal antibody, and a steroid. Many people who are fit enough are also considered for a stem cell transplant using their own cells, either soon after diagnosis or later. Ask your team to walk through why a specific combination and timing were chosen for your stage and risk category.
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Written by: Cancer ExplainedSources last checked: 2026-08-13 what this meansLast updated: 2026-08-16Next planned review: 2027-07-23
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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