Response to treatment

During treatment for multiple myeloma, your healthcare team will monitor you closely to understand how treatment is working. This is often described as response to treatment. Monitoring for response to treatment may include:

• blood tests
• urine tests
• imaging tests

Response to treatment is usually measured after the first round of treatment and again after each round until the healthcare team sees a trend in the response. After that it may be measured less frequently as long as there is no change in the measured response (called a plateau).

The International Myeloma Working Group groups the response to treatment into the following categories.

A stringent complete response (sCR) means that all of the following are true:

• There is a complete response.
• The serum free light chain ratio is normal.
• There are no myeloma cells in the bone marrow.

A complete response (CR) means that all of the following are true:

• Immunofixation (a specialized type of electrophoresis that identifies the type of M-protein or immunoglobulin light chain) does not find M-protein in the blood or urine.
• An extramedullary plasmacytoma disappears.
• Myeloma cells make up less than 5% of the cells in the bone marrow.

A very good partial response (VGPR) means that either of the following is true:

• Immunofixation finds M-protein in the blood or urine, but M-protein isn’t found by standard electrophoresis.
• The M-protein level in the blood has decreased by 90% or more, and the M-protein level in the urine is less than 100 mg (in urine collected over 24 hours).

A partial response (PR) means that both of the following are true:

• The M-protein level in the blood has decreased by 50% or more.
• The M-protein level in the urine has decreased by 90% or more or is less than 200 mg (in urine collected over 24 hours).

If the M-protein levels in the blood and urine can’t be measured, a PR is defined by a decrease of 50% or more between the uninvolved and involved free light chain (Bence-Jones protein) levels.

If the M-protein and free light chain levels can't be measured, a PR is defined by a decrease of 50% or more of myeloma cells in the bone marrow (if the baseline bone marrow myeloma cell percentage was 30% or more).

In addition to the above criteria, if there was an extramedullary plasmacytoma found at the time of diagnosis, it has shrunk by 50% or more.

Progressive disease (PD) means that at least one of the following is true:

• The M-protein level in the blood has increased by 25% or more.
• The M-protein level in the urine has increased by 25% or more.
• If the M-protein levels in the blood or urine are not measurable, the absolute increase in the difference between the involved and uninvolved free light chain levels must be greater than 10 mg/dL.
• Myeloma cells make up 10% or more of all cells in the bone marrow.
• Plasma cells make up 5% or more of the cells in a blood smear test.
• There are new abnormal areas in the bone or extramedullary plasmacytomas.
• Abnormal areas in the bone or extramedullary plasmacytomas have increased in size by 50% or more.

• Multiple myeloma is causing a high level of calcium in the blood (called hypercalcemia).

Stable disease (SD) means that the cancer does not meet the criteria for a stringent complete response, a complete response, a very good partial response, a partial response or progressive disease.

Relapsed disease, or a clinical relapse, means that at least one of the following is true:

• There is evidence that the disease is getting worse or you have CRAB symptoms or both.
• There are new abnormal areas in the bone or extramedullary plasmacytomas.
• Abnormal areas in the bone or extramedullary plasmacytomas have increased in size by 50% or more.
• Multiple myeloma is causing a high level of calcium in the blood (called hypercalcemia).
• There is a decrease in hemoglobin levels in the blood by 2 mg/dL or more that isn't due to treatment or other conditions not related to multiple myeloma.
• There is an increase in creatinine levels in the blood by 2 mg/dL or more.

• The blood is thick due to abnormal proteins in the blood (called hyperviscosity).

Refractory disease is cancer that didn't respond to treatment. Another way of describing refractory cancer is to say that it is resistant to a treatment. The cancer may be resistant from the start of the treatment, or it may become resistant during treatment.