response to treatment

When reading about myeloma – particularly myeloma research – you may hear terms such as “Complete Response” (CR) or “Partial Response” (PR).  Different studies may use different definitions, so check the study for what it is using.  The International Myeloma Working Group response categories are:
 
sCR (stringent Complete Response): Complete Response (see below) plus normal free light chain ratio and an absence of clonal cells in the bone marrow by immunohistochemistry or immunofluorescence. 

CR (Complete Response): Negative immunofixation in the serum and urine, disappearance of any soft tissue plasmacytomas and five percent or less of plasma cells in the bone marrow.

VGPR (Very Good Partial Response): Serum and urine M-protein detectable by immunofixation but not on electrophoresis or 90% or greater reduction in serum M-protein plus urine M-protein less than 100 mg per 24 hours.

PR (Partial Response): Fifty percent or greater reduction in the serum M-protein and a reduction in the 24-hour urinary M-protein of 90 percent or more, or to less than 200 mg per 24 hour.  If the serum and urine M-protein are unmeasurable, a 50% or greater decrease in the difference between involved and uninvolved free light chain levels is required in place of the M-protein criteria.  If serum and urine M-protein are unmeasurable and serum free light assay is also unmeasurable, a 50% or greater reduction in plasma cells is required in place of M-protein, provided baseline bone marrow plasma cell percentage was 30% or greater.  In addition to these criteria, if present at baseline, a 50% or greater reduction in the size of soft tissue plasmacytomas is also required.

SD (Stable Disease): Not meeting the criteria for CR, VGPR, PR or progressive disease.  SD is not recommended for use as an indicator of response, as the stability of disease is best described by estimating the time to progression.

PD (Progressive Disease): Requires one or more of the following:
          • Increase of 25 % or more from baseline in:
               - serum M component and/or urine M component and/or bone marrow plasma cell percentage
                (the absolute percentage must be equal to or greater than 10 %)
               - development of new bone lesions or plasmacytomas
               - development of hypercalcemia attributable to the plasma cell disorder

Since relapses are common in myeloma, you and your health care team have to think about not only your immediate needs -- but also what you might want to do in the future.  Talk with your doctor and your healthcare team about how you can keep your options for future treatments as open as possible.