Read about stem cell transplants and how they are used to treat some types of cancer.
What stem cell transplants are
A stem cell transplant aims to try and cure some types of blood cancer such as leukemia, lymphoma and myeloma. It is also called a peripheral blood stem cell transplant.
You have very high doses of chemotherapy, sometimes with whole body radiotherapy. This has a good chance of killing the cancer cells but also kills the stem cells in the bone marrow.
Stem cells are very early blood cells in the bone marrow that develop into red blood cells, white blood cells and platelets.
We need stem cells in order to survive. Doctors can collect stem cells from your blood or a donor's. After high dose treatment, you have the stem cells into a vein through a drip to replace those that the cancer treatment has killed.
Stem cell transplant means that you can have higher doses of treatment. So there may be more chance of curing the cancer than with standard chemotherapy.
Having your own stem cells
You might have your own stem cells given back to you after high dose treatment. This is called an autograft.
You have growth factors before, and sometimes after, a stem cell transplant. Growth factors are natural substances that make the bone marrow produce more stem and blood cells. You have them as small injections under the skin.
You have daily injections of growth factor for between 5 and 10 days. Sometimes you may have low doses of a chemotherapy drug alongside the growth factor injections.
The chemotherapy and growth factor injections help your bone marrow to make lots of stem cells. These stem cells then spill out of the bone marrow into the bloodstream.
Growth factor injections can cause some side effects. Some people have itching around the injection site. Some people get a high temperature (fever). You might have some pain in your bones after you have had a few injections.
This is because there are a lot of blood cells being made inside the bones.
Collecting the stem cells
After your growth factor injections, you have blood tests every day to see if there are enough stem cells in your bloodstream. When there are enough cells, you have them collected. This is called harvesting.
Collecting the stem cells takes 3 or 4 hours. You are awake during this process. You lie down on a couch. Your nurse puts a drip into each of your arms and attaches it to a machine.
Your blood passes out of one drip. It goes through the machine and back into your body through the other drip. The machine filters the stem cells out of your blood. They are collected and frozen until after your high dose treatment.
You might feel very tired after having stem cells collected. Your calcium level might also get low during your collection, which means you may have:
- tingling around your mouth
- muscle cramps
Having stem cells from a donor
Some people have stem cells from another person. These are called donor stem cells. They are collected from the donor in the same way described above.
If you have donated stem cells they need to closely match your own. A brother or sister is most likely to be a close match.
Sometimes, if you don't have a brother or sister (a sibling donor) who is a match, you can have stem cells from a donor who is not related to you but whose stem cells are similar to yours. This is called a matched unrelated donor (MUD) transplant.
Matching donor stem cells
First, laboratory staff check the surface of your blood cells and the donor blood cells for certain proteins. The proteins are called HLA markers or histocompatibility antigens. So the test is called HLA typing or tissue typing.
Everyone has their own set of proteins. Staff compare the proteins on the cells in the blood samples to see if the HLA markers are the same or very similar. Usually 10 HLA markers are checked.
The results of your blood test and the donor's test tell your doctor how good the HLA match is between you. Members of your close family are most likely to have similar proteins to yours.
You can have a transplant without a perfect match. This is called a mismatched transplant.
If you have a mismatched transplant, you are more likely to have a reaction afterwards. The reaction is called graft versus host disease (GVHD). This means the immune cells from the donated stem cells attack some of your body cells.
GVHD typically causes skin rashes, diarrhoea and liver damage. You will have anti rejection drugs to help stop it developing. GVHD can be severe and even life threatening for some people. But mild GVHD can also be helpful for some people. It is an immune system reaction and can help to kill off any cancer cells left after your treatment.
Your doctor may consider a half matched transplant (haplo identical transplant). This means the donor is at least a 50% match with you. This could be one of your parents, a sibling or your child.
In the past these transplants have been difficult to do due to the increased risk of severe GVHD and infection. But doctors are finding new ways of improving this type of transplant and reducing the risk of GVHD.
Cord blood stem cells
You might have a stem cell transplant using stem cells from umbilical cord blood. Doctors take blood from the umbilical cord and placenta that is very rich in stem cells. The blood bank may give the donated stem cells to a person whose blood cells closely match the donated cells.
Cord transplants are mostly used for children because a smaller amount of cells are collected. You could have a stem cell transplant from 2 different umbilical cords. This is called a double cord transplant.
Stem cells can be used in mini transplants. These are also called reduced intensity conditioning (RIC) transplants. You have lower doses of chemotherapy than in a traditional stem cell transplant. So you might have this treatment if you are not fit or well enough for a traditional transplant.
Help for you
The Anthony Nolan charity has helpful information. They have a register to match people willing to donate their bone marrow or blood stem cells to people who need transplants. They also provide information, support and an online forum for patients and families going through a transplant.