Hello Helen
When you are first diagnosed then the BMB serves a number of functions including taking a sample for cytogenetic testing as well as assessing the percentage of abnormal plasma cells in the bone marrow. It is a snapshot of the area where the sample was taken.
The myeloma is not always evenly distributed throughout the skeletal structure, an MRI/ PET scan can be used to show this picture better.
But after induction treatment before SCT they will want to know how much the abnormal plasma cells have reduced in the bone marrow. Light chain values from blood samples are good for regular monitoring during ongoing treatment to assess degree of disease control or determine if relapse is setting in, but do not give a picture of how much myeloma is still in the bone marrow- hence the BMB.
After SCT the BMB gives a picture of just how much of the cancer has been removed by this treatment. A stringent complete response will indicate negative disease status at bone marrow level, (although there is always some myeloma around it is at an undetectable level), as well as normal blood values for your light chains. There are guidelines written to inform our doctors just what degree of remission has occured from the information collected this way.
No need to be confused the BMB serves a purpose at particular times with blood levels of light chains measured for ongoing routine monitoring- no one wants regular BMB’s!