How many cells do you aim to collect during the harvesting process?
Why are extra stem cells collected for later use?
How can these stem cells be used in the future?
Different transplant centers will have different thresholds for what the proper number of stem cells are.
But lots of studies suggest having a minimum of 2 million stem cells per kilogram body weight.
We use a marker called CD34, on the surface of the cells, we measure CD34 cells in the blood, and if we have about 2 million per kilogram of body weight, we think that's enough for one transplant.
We have done transplants with a little less than that and patients do just fine.
So for two transplants, I typically try to collect at least 4 million per kilogram.
And whenever we can get a little bit more, we're always happy to do that.
So some centers use a little bit more like 3 to 5 million, but that's a typical range.
That is a very good question and that's something that you should ask.
Normally there is a minimum number of stem cells that is required to restore your bone marrow function after a transplant.
And that's usually about 2 million cells.
Most of us like to give a little bit of a cushion in case not all of the cells are perfectly viable.
So we tend to give at least 3 to 5 million cells, and that is for one transplant.
Myeloma is the one disease where sometimes a second transplant is helpful.
Both at following immediately following the first transplant and called tandem transplants or perhaps in the future at a time of relapse.
And so for the most part, you should be collecting for at least two transplants.
So generally we have we are storing enough for three stem cell transplants for the majority of our patients, the only exception would be patients who are in their seventies.
And in that situation where we are storing for two.
The goal number of cells that is set by the team that is in charge of the procedure is based on the patient's size.
And based on this hope that we'll be able to collect enough stem cells for two different procedures.
If the patient has a single stem cell transplant and never needs to use those cells again for a transplant, there is the potential that those stored cells could be used in the future if something changes with their condition and their bone marrow, for whatever reason, isn't working as well.
In some instances, people who have had CAR-T therapy, that newer type of immunotherapy, which is another cellular therapy treatment, have had long periods of time where their blood cells can remain very, very low.
And sometimes we have used those stored stem cells in that setting to give them a little bit of a boost to help bring up those stem cell numbers again.
How long can stored stem cells be preserved?
I think that we don't necessarily know.
I absolutely have patients who have cells that have been stored for more than ten years.
And what we do at our institution is we freeze small sections of the cells separately from the main batch of cells.
And then if there's interest in using a stored cell product that might be quite old, you can thaw out that little bit of the cell product.
a guess as to whether the rest of the product is going to be is going to going to work.
HealthTree • May 27, 2025
