In a typical stem cell transplant for cancer very high doses of chemo are used, often along with radiation therapy, to try to destroy all the cancer cells. This treatment also kills the stem cells in the bone marrow. Soon after treatment, stem cells are given to replace those that were destroyed. These stem cells are given into a vein, much like a blood transfusion. Over time they settle in the bone marrow and begin to grow and make healthy blood cells. This process is called engraftment.

There are 3 basic types of transplants. They are named based on who gives the stem cells.

These stem cells come from you alone. In this type of transplant, your stem cells are taken before you get cancer treatment that destroys them. Your stem cells are removed, or harvested, from either your bone marrow or your blood and then frozen. To find out more about that process, please see the section Whats it like to donate stem cells? After you get high doses of chemo and/or radiation the stem cells are thawed and given back to you.

One advantage of autologous stem cell transplant is that you are getting your own cells back. When you donate your own stem cells you dont have to worry about the graft attacking your body (graft-versus-host disease) or about getting a new infection from another person. But there can still be graft failure, and autologous transplants cant produce the graft-versus-cancer" effect.

This kind of transplant is mainly used to treat certain leukemias, lymphomas, and multiple myeloma. Its sometimes used for other cancers, like testicular cancer and neuroblastoma, and certain cancers in children. Doctors are looking at how autologous transplants might be used to treat other diseases, too, like systemic sclerosis, multiple sclerosis, Crohn disease, and systemic lupus erythematosis.

A possible disadvantage of an autologous transplant is that cancer cells may be picked up along with the stem cells and then put back into your body later. Another disadvantage is that your immune system is still the same as before when your stem cells engraft. The cancer cells were able to grow despite your immune cells before, and may be able to do so again.

To prevent this, doctors may give you anti-cancer drugs or treat your stem cells in other ways to reduce the number of cancer cells that may be present. Some centers treat the stem cells to try to remove any cancer cells before they are given back to the patient. This is sometimes called purging. It isnt clear that this really helps, as it has not yet been proven to reduce the risk of cancer coming back (recurrence).

A possible downside of purging is that some normal stem cells can be lost during this process, causing the patient to take longer to begin making normal blood cells, and have unsafe levels of white blood cells or platelets for a longer time. This could increase the risk of infections or bleeding problems.

One popular method now is to give the stem cells without treating them. Then, after transplant, the patient gets a medicine to get rid of cancer cells that may be in the body. This is called in vivo purging. Rituximab (Rituxan), a monoclonal antibody drug, may be used for this in certain lymphomas and leukemias, and other drugs are being tested. The need to remove cancer cells from transplants or transplant patients and the best way to do it is being researched.

Doing 2 autologous transplants in a row is known as a tandem transplant or a double autologous transplant. In this type of transplant, the patient gets 2 courses of high-dose chemo, each followed by a transplant of their own stem cells. All of the stem cells needed are collected before the first high-dose chemo treatment, and half of them are used for each transplant. Most often both courses of chemo are given within 6 months, with the second one given after the patient recovers from the first one.

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Types of stem cell transplants for treating cancer