How do light chain myeloma responses differ from heavy chain responses?
Regarding light chain myeloma versus heavy chain myeloma and the responses, my experience has been that light chains change more rapidly than heavy chains. So if you've got really high free light chain production, you're probably going to see those levels either go up or go down faster than you're going to see the heavy chain. That's not always the case. There are some people with myeloma where the heavy chain really is the predominant thing, and it just takes a lot longer for the big heavy chain to clear than it does for the light chains to clear. But that doesn't necessarily indicate what's going on with the myeloma cells themselves. All that that has to do with is what they're making.
And I would say that the more important thing—I mean, we love to see the numbers going down—but the more important thing is, is the cancer growing? Is the cancer shrinking? Is the cancer staying stable? And the numbers help us to figure that out. But it's not a race to get the numbers the lowest that they can be. The goal is to keep it under control as long as possible.
So, yes, there's a little bit of a difference. But in the end, there is no big difference between the two types. It's just how quickly the numbers change. Light chain is a little bit more sensitive. And because the half-life of the light chain is very short, you can run off the light chains quickly and within 3 to 7 days, you can see changes in the light chains coordinating with their response to treatment.
In the relapsed setting, I think light chain alone is not enough to change treatment and it's not enough listed. Really, the kappa and lambda ratio, if the range would be very high. Anything less than ten is not accepted. And to go from clinical trials. So minor changes, I know patients would be very anxious if the light chains go from 1.6 to 2.5. That change is not significant by any means and should be followed. And we're really not starting from a slight change, as I said, until we reach eight and ten difference.
