Stem Cell Transplant for Chronic Lymphocytic Leukemia (CLL)

A stem cell transplant (SCT) allows doctors to use higher doses of chemotherapy (chemo) and/or radiation therapy to treat some types of cancer. This is sometimes an option to treat chronic lymphocytic leukemia (CLL), although it’s not common.

Why might a stem cell transplant be useful for CLL treatment?

A stem cell transplant can be used to treat some types of leukemia, including CLL (although this is not common).

For this treatment, doctors use very high doses of chemotherapy (sometimes along with radiation) to destroy the cells in a person’s bone marrow, including the leukemia cells. After these treatments, the person gets a transplant of blood-forming stem cells to restore the cells in their bone marrow.

Targeted drugs, chemotherapy, and/or immunotherapy are usually very helpful in treating CLL and improving symptoms. These treatments can often control CLL for a long time. But sometimes CLL might not respond to these treatments, or they might stop working over time.

Where do the stem cells for a transplant come from?

Blood-forming stem cells used for a transplant can come from:

• Blood (called a peripheral blood stem cell transplant or PBSCT)
• Bone marrow (called a bone marrow transplant or BMT)
• Umbilical cord blood

Bone marrow transplant was more common in the past, but today it has largely been replaced by PBSCT.

When is a stem cell transplant used for CLL?

It's not yet clear exactly how helpful stem cell transplants are in people with CLL, so when a transplant is done, it's often as part of a clinical trial.

Some situations in which an SCT might be considered include:

• To treat CLL that comes back after treatment or is no longer responding to standard treatments, especially if it's a type of CLL that's harder to treat, such as if the cells have a chromosome 17 deletion or a TP53 gene mutation.
• To treat CLL that has transformed into a more aggressive type of leukemia.

Types of stem cell transplants

The main types of stem cell transplants are:

Allogeneic SCT

Allogeneic SCT is the most common type of stem cell transplant used to treat CLL.

In an allogeneic transplant, the stem cells come from someone else (a donor). To lower the chance of serious health problems, your donor needs to match you in terms of tissue type.

A close relative, like a brother or sister, is often a good match. Less often, a matched unrelated donor may be found.

This type of transplant can cause severe or even life-threatening complications and side effects, so it's often not a good option for people who are older or have other serious health problems.

Non-myeloablative transplant (mini-transplant)

A non-myeloablative transplant might still be an option for people with CLL who are older or have other health issues and can’t tolerate the high doses of chemo used for a standard allogeneic transplant. This procedure is also known as a mini-transplant or reduced-intensity transplant.

For this type of transplant, you get lower doses of chemo and radiation that don’t completely destroy the cells in your bone marrow. You then get the allogeneic (donor) stem cells. These cells enter your body and establish a new immune system, which sees the leukemia cells as foreign and attacks them (a graft-versus-leukemia effect).

Autologous SCT

Autologous SCT is rarely used to treat CLL.

For an autologous transplant, your own stem cells are collected from your blood or bone marrow before treatment. They are frozen and stored while you get treatment with high-dose chemotherapy and/or radiation.

In the lab, a process called purging may be used to try to remove any leukemia cells in the samples. The stem cells are then put back (reinfused) into your blood after treatment. One problem with this type of SCT is that there might be remaining leukemia cells that are given back to you along with your stem cells.