How is the overall myeloma protein level in the blood affected by its distribution?

How is the overall myeloma protein level in the blood affected by its distribution?


This week’s Ask Dr. Durie is rather a technical
question. The questioner asks, “How are the myeloma
protein levels impacted by distribution of the proteins within the body and even passing
out into the urine?” Well, it may not seem like it, but this is
actually rather an important question. Because IgG, IgA, and light-chains, some of
the main monoclonal proteins, or the myeloma-related proteins that are produced by the myeloma
cells, pass through the bloodstream and frequently fragments come out in the urine. But along the way, the body breaks down these
proteins, and also the proteins leak out into the tissues of the body. So this does impact the levels in the blood. So why is that important? Well it’s quite important, for example,
for IgG. IgG has what’s called a half-life, so that
the level drops in half in about three weeks. So what does that mean? Well, it means that if your treatment is working
fantastically well, the IgG that is in your blood, will not disappear overnight. It still be, half of it, will still be there
in three weeks. So you should not be disappointed if your
IgG level does not plummet, because it’s going to take a little bit of a lag time for
those IgG levels to drop. Now IgA levels, they drop a little bit faster. And the Bence Jones, or the light chain levels,
the kappa and lambda light chain levels, actually drop rather quickly—within ten to twelve
hours—they drop in half. So you can see a response in a light-chain
myeloma within a day or two, you can see those levels actually plummet, as compared to the
IgG. But what is true for all of the proteins is
that once they get down to low levels, the breakdown, what we call the metabolism, or
catalyze metabolism. The breakdown of those proteins in the blood
and by the kidneys into the urine, it slows down. So there is a very long period of time between
the levels being low and actually getting down to zero. So what is the bottom line here? The BOTTOM LINE is that it is important to
be patient in looking at the protein levels. They do take a little bit of time to drop. And especially at the low levels, it takes
time for the immunofixation level, that IFE test, which is the crucial level that can
be coming negative. It is important to have a little bit of patience
and wait for that to turn to zero, over a period that could be one, two, or three months And this is very important in terms of MRD
testing, because we like that level to be truly zero before we go ahead and put a patient
through a bone marrow test to see if they might be MRD negative. Just to be aware that levels can be a little
bit misleading and maybe even a little bit disappointing early on. It takes time for them to drop to those very,
very lowest levels. Kind of a crazy question. A little bit of a technical question. But you can learn a lot from trying to understand
these aspects of the disease.

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