A bone marrow transplant is an amazing process, involving both the miracle of natural processes and medical science. A stem cell transplant is a version of a bone marrow transplant, which I'll explain below.
I am a leukemia patient scheduled for a stem cell transplant within the next three weeks, which will replace my bone marrow.
I am not a doctor. This is just a general overview of bone marrow transplants based on my research and what I've been told by the nurses and doctors who are treating me. It is written from the perspective of someone who is about to go through one!
All your blood cells are made in your bone marrow. When you're born, all your bones have marrow. As you age, your bones stiffen, and only your hips, torso, and cranium have marrow.
There are three types of blood cells:
Your bone marrow has stem cells. A stem cell (or "pluripotent" cell) is a cell that can become other types of cells. Infant stem cells can become any type of cell in the body. Your bone marrow cells, however, are what are known as hematopoeitic stem cells. They can become only blood cells, but they can become any kind of blood cell.
In diseases like leukemia and lymphoma, a cell in the bone marrow becomes cancerous. Usually, it stops at an immature stage of development, then begins reproducing. Cancerous cells lose their ability to die when they're supposed to (a process called apoptosis). Thus, they begin either to crowd out other cells in the bone marrow or in the blood stream or both.
There are two major types of leukemia, chronic and acute. Acute leukemia progresses quickly and requires extreme and rapid intervention. Usually that is chemotherapy and possibly a bone marrow transplant, which will be explained in a moment.
Chronic leukemia is more slow-moving. It is treated with medications. If I understand correctly (and I might not because I have acute leukemia), doctors normally don't treat it with a bone marrow transplant because the transplant and preparation for it are more likely to be fatal than the leukemia is!
I'm going to focus on acute leukemia.
Untreated, acute leukemia can kill in weeks. I saw a statistic that said that in 1966 the mean survival time was 40 days from diagnosis. Personally, I needed a transfusion of blood 19 days after I was diagnosed. Based on the decline of my blood cells, I'm pretty sure I would not have lived more than 6 weeks after my diagnosis if I had not been treated.
The proliferation of cancerous marrow and blood cells are initially treated with chemotherapy. The treatment destroys blood cells and marrow cells. The patient is given blood treated with radiation to remove all white blood cells. The red blood cells keep the patient alive.
The idea is to destroy pretty much all the white blood cells, which are almost always the ones that are cancerous, and most of the marrow cells. The hope is that in the process all the cancerous cells will be destroyed.
Once chemotherapy is over, the marrow is allowed to grow back and begin producing blood again. Hopefully, at this point, the marrow and blood system will be restored without cancer.
Often the chemotherapy is repeated three or four times to ensure destruction of all the cancer cells.
Chemotherapy is dangerous. For two to three weeks the patient has no white blood cells, making him or her extremely vulnerable to infections. Extreme care is maintained to keep the patient safe, and antibiotics and other prophylactic medications are given.
In many cases, this is enough to cure the leukemia, and the patient lives the rest of his or her life completely healthy.
If the patient relapses, then the next step is a bone marrow transplant. Also, in some forms of leukemia the risk of relapse, and the danger associated with it, is so high that a transplant is warranted even before relapse occurs. (Such is the case with me.)
If chemotherapy doesn't work or is known not to be enough, then there is one step further that treatment can go. The bone marrow can be replaced by someone else's.
This can be done in two ways. One way is called a stem cell transplant, and it's basically a "short cut" for the donor. I'll explain that in the next section.
In a bone marrow transplant, bone marrow is extracted from the hips of the donor. About a hundred tiny holes are made through the skin into the hip bone with a special tool that punches a small hole in the bone. A needle is inserted through the hole (it's possible the needle is part of the tool) and bone marrow is sucked out of the bone.
Bone marrow is mostly liquid. It looks a lot like blood.
The holes in the skin are so small that no stitches are needed. The bone heals up in about a week. I'm told that the donor will feel like a mule kicked them in the rear end, and they'll hurt for about a week.
The process, at least of the transplant itself, is much easier on the recipient. About a quart of marrow is pulled from the donor, and it is given to the recipient intravenously.
Yes, that's right. The donor spends a few minutes (I'm told), getting the bone marrow by IV.
That is what is so amazing. The bone marrow simply goes in a vein, and it takes care of the rest from there. It makes its way to the bones and takes up residence as the new bone marrow. From there it produces an entirely new blood system. In fact, it is possible for the recipient's blood type to change!
The recipient's blood type can change because the doctors do not match the donor for blood type. Instead, if the donor is a sibling (brother or sister), there are six places on the recipient and donor's DNA that have to match. If the donor us unrelated, then there are four more things to consider. I actually don't know whether those four things are four more DNA spots.
I'll explain partial matches below. I'll also explain the dangerous and difficult preparation that the recipient has to go through in order to receive the transplant, but first let's explain a "stem cell" transplant.
A stem cell transplant is just a different way to replace the bone marrow. It's an easier route for the donor.
In a stem cell transplant, the donor is given a series of growth hormone shots over several days. This causes the bone marrow to rapidly produce the hematopoeitic stem cells that are the precursors to all the blood cells. So many stem cells are produced that some stem cells are forced out of the marrow and into the blood stream.
After five days or so, the donor is hooked up to a machine that removes blood through a vein on the donor's arm. The blood is run through the machine, which somehow removes the stem cells. Once the stem cells are removed, the blood is put back into the donor in his or her other arm.
The stem cells are then taken to the recipient and given by IV just as the bone marrow would be. It works exactly the same way, just as amazing.
With some forms of leukemia, or if no match can be found, a patient can be put into remission with chemo so reliably that their own stem cells can safely be harvested for a later transplant.
For example, I am emailing a Blastic Plasmacytoid Dendritic Cell Neoplasm patient, a leukemia very similar to my "undifferentiated" leukemia. A year and a half ago, he received an "autologous" stem cell transplant because no marrow donor could be found who matched him.
Because he was in such good health and only age 44, he was able to endure multiple rounds of chemotherapy. After the fourth round, they harvested his stem cells in the way described above, and after the eighth round of chemo, they gave his cells back to him as a transplant.
So far, so good. If you're a Christian, please pray for him. His name is Michael.
Bone marrow can be obtained from a sibling even if the sibling only matches on 3 of the 6 spots on the DNA that I mentioned above. With a stranger, doctors want to have at least a 9 out of 10 match. That includes the 6 spots on the DNA and the other 4 things, which I don't know what they are.
A partial match presents a problem because the new bone marrow will produce a new immune system that is not a very good match for the patient. Thus, the new immune system is very likely to attack the body of the recipient.
Over time, the immune system apparently gets used to the body it's in, but the process is long and difficult, sometimes taking years and always taking at least 3 to 6 months.
The preparation for receiving the transplant is also arduous, involving almost complete destruction of the bone marrow so that it can be replaced. The almost complete "ablation" also serves the purpose of ensuring all the cancer cells are destroyed (hopefully).
However, in a partial match the trauma of the transplant combined with the trauma of the bone marrow ablation is usually too much. It could easily kill the patient. Thus, partial matches are normally "non-myeloablative." In other words, they don't destroy all the bone marrow. They only ablate as much as is needed to ensure the transplant takes effect.
When a non-myeloablative transplant is done, the doctors hope that the new immune system will find and destroy whatever leukemic cells are left. This is a real possibility, and it is often successful. If it's not successful, the patient will relapse, which will probably result in death.
I have been in communication with a man on the east coast who had a non-myeloablative transplant for Blastic Plasmacytoid Dendritic Cell Neoplasm. He has been healthy for 3 years now.
I am getting a briefing from the nurse practitioner in charge of my case tomorrow concerning the transplant, so maybe I should be waiting until tomorrow to write this!
I have seen all the paperwork that I have to sign, though, so I think I have all the information that would need to go on a web page like this.
As I've already said, the point of the preparation is to reduce the bone marrow so much that it can be replaced by the transplant. Also, the preparation is one more attempt to insure that all or almost all the leukemic cells have been destroyed.
For me, and from others I've talked to, my regimen is typical, this means five days of intense chemotherapy. My paperwork says my therapy is "reduced intensity," so some people must get even stronger drugs. I've not heard of any cases of anyone receiving chemo for a longer period to prepare for transplant.
On day 6 I will receive a full body radiation. This, I'm guessing, is for two purposes. One, it can destroy any cancer cells not reached by the leukemia. Two, it can help kill any lingering diseases that have been kept at bay by my current immune system. When my bone marrow is replaced, my immune system will be brand new. It will not have any of the immunities of my current immune system, and a former case of, say, chicken pox, that is not completely eradicated could come roaring back.
On day 7, I will receive the transplant. On days 5 and 7, I will also receive drugs to suppress the last vestiges of my current immune system. This will help my bone marrow and immune system not to compete with the new one, and it will begin the process of protecting me from the new immune system should it decide to attack my body.
In a typical organ transplant, the patient has to worry that his body's immune system will reject the organ. In a bone marrow transplant, it is the immune system that is being replace. You have to worry about the transplant, the immune system, rejecting the body!
This brings us to the dangers of a bone marrow transplant.
The risks of a bone marrow transplant vary with age. The healthier you are, the better you will handle the trauma of the chemotherapy. Also, the healthier you are, the more likely you will survive the trauma of infections or diseases that you may pick up while you have no immune system.
The chemotherapy is the first and greatest problem. Chemo medications are poisons. They destroy quickly reproducing cells, which allows them to target cancer cells. But cancer cells are not the only quickly reproducing cells in the body. Mucous cells, blood cells, and marrow cells are destroyed.
Because the white blood cells are destroyed, there is a real danger of infections. Pneumonia especially is a problem. Not only does the patient have to worry about pathogens from outside, but he has to worry about pathogens that he carries around all the time. Almost everyone has staphylococcus bacteria on their skin. That's no big deal when you have an immune system, but it can be a real danger when the immune system is silenced.
Only about 50% of patients with acute leukemias similar to mine make it through the first round of chemotherapy. The rest either die from complications, or the chemo doesn't work, and the cancer is not stopped.
Only so many attempts can be made to stop leukemia with chemotherapy because the chemo medications are so toxic. Repeated attempts can damage the heart, but they are especially dangerous to the liver. Third and fourth attempts to put leukemia in remission are only occasionally attempted and they are not often successful.
I'm past the remission stage, so here's what the paperwork has to say about my current chances.
According to the paperwork I have a 20-30% chance of dying from complications related to the chemotherapy given to prepare me for the transplant.
The next danger is that the transplant won't "engraft." If the new marrow doesn't grow in my bones, that will almost certainly be fatal. That rarely happens, however. A nurse who has participated in over 1,000 transplants told me that she's only seen 2 fail to engraft.
Once the transplant "takes," the final danger is that the new immune system will attack my body. The chances of this happening on a mild basis are very high, 75 to 80%. However, this can usually be controlled with medication, and the odds of my being killed by "Graft-versus-Host Disease" (GVHD) are about 20%, if I am one of the 75 to 80% who face it.
I did some math. Since this is a two-step process, it's not as simple as adding the GVHD risk to the preparatory regimen risk. The odds, according to the paperwork I have to sign tomorrow, of this treatment killing me are between 32% and 42.8%.
Part of the problem with GVHD is that the treatment for it involves suppressing the immune system. This is the kind of thing that organ transplant recipients live with all their life. For a bone marrow transplant recipient, it's possible for the GVHD to come to an end as the new immune system gets used to its new body, eliminating the need for immunosuppressive drugs.
My particular transplant is coming from cord blood, which is blood from an umbilical cord and placenta that someone donated after a birth. (Thank you!!!)
Usually, one cord and one placenta does not produce enough stem cells to transplant an adult. Therefore they usually use two cords a special process that multiplies the stem cells. (I don't know anything about this process; I just read a news report saying there is one.)
Cord blood does not have to match anywhere near as exactly as marrow or stem cells from an adult. Because the immune system of an infant is undeveloped, it is much less likely to attack its new host. There still must be a match, but it does not have to be as exact as an adult match, which is how it is possible that they could find two cords from which to give me blood.
My friend in Ireland, mentioned above, who got the autologous stem cell transplant was unable to get cord blood because he was too big! He is something like 6'5" and 225 pounds. Apparently, it's fortunate that I'm only 5'8".
Once the new immune system is in, the doctors will automatically suppress it for three months. After three months, evaluation will be made based on how much Graft-versus-Host Disease I've had. If there's been none or it's been very mild, then they will begin to wean me off the immunosuppressives. However, GVHD can flare up after that, too, which will lead to increasing the drugs again.
After a year, if the new immune system is off the immunosuppressives, then I will need to have all my immunizations again. All of the immunities I have gained through my life will be gone. I suppose that now I'll have to regard the yearly flu shots as more important than I ever have before. Most of us accumulate several flu immunities throughout our life. I haven't had the flu in years, and I'm not looking forward to welcoming it back.
Well, that's about all I can think of to tell you about bone marrow and stem cell transplants. I hope you found that as interesting as I have found the whole process.
Don't forget you can follow my journey at Thrilled to Death. I'm told it's very inspiring. I'm one of those people who believe that all things work together for good to those who love God and are called according to his purpose, just like the apostle Paul said (Romans 8:28).