The period after treatment when a WM patient has experienced either stabilization of disease, an improvement in disease status, or even, unfortunately, disease progression is called a “response”. While an improvement in disease status is sometimes commonly referred to as a “remission”, the preferred scientific terminology is “response”.
Response to treatment and duration of response vary widely in WM. Currently, there is no way to accurately predict how good or how long a response will be for an individual patient. One of the goals of WM researchers is to better determine how patients will respond to a particular treatment based on the variations in each person’s disease biology and unique genetic makeup.
Caution is advised in the early evaluation of response during rituximab-based therapy (or other anti-CD20 monoclonal antibodies) because of the common “IgM flare,” which is a temporary increase in IgM but does not necessarily imply disease progression. In most cases it will resolve, but additional tests may be performed to determine if this increase is a temporary condition or disease progression.
The Sixth International Workshop on Waldenstrom’s Macroglobulinemia in 2010 updated the following definitions of response to treatment as follows:
- Complete response (CR) – Absence of serum monoclonal IgM by immunofixation, normal serum IgM level, complete resolution of enlarged lymph nodes and enlarged spleen if present at baseline, normal bone marrow aspirate and biopsy.
- Very good partial response (VGPR) – Monoclonal IgM protein is detectable, equal to or greater than a 90% reduction in serum IgM level from baseline, complete resolution of enlarged lymph nodes and enlarged spleen if present at baseline, no new signs or symptoms of active disease.
- Partial response (PR) – Monoclonal IgM protein is detectable, equal to or greater than 50% but less than 90% reduction in serum IgM level from baseline, reduction in the size of enlarged lymph nodes and enlarged spleen if present at baseline, no new signs or symptoms of active disease.
- Minor response (MR) – Monoclonal IgM protein is detectable, equal to or greater than 25% but less than 50% reduction in serum IgM level from baseline, no new signs or symptoms of active disease.
- Stable disease (SD) – Monoclonal IgM is detectable, less than 25% reduction and less than 25% increase in serum IgM level from baseline, no progression in enlarged lymph nodes or enlarged spleen if present at baseline, no new signs or symptoms of active disease
- Progressive disease (PD) – Equal to or greater than 25% increase in serum IgM level from lowest point (requires confirmation) and/or progression in clinical features attributable to disease.
In the scientific literature, one may see the term objective response, which is a statistical term combining the number of complete and partial responses.
