Stem Cell Transplant for Chronic Lymphocytic Leukemia

Most often, targeted drugs, chemotherapy, and/or immunotherapy are very helpful in treating CLL and improving symptoms. These treatments can often control CLL for a long time. But even if all signs of leukemia go away, CLL often comes back later.

Higher doses of chemo might work better, but they often can't be used because they could severely damage the bone marrow, where new blood cells are made. This could lead to life-threatening infections, bleeding, and other problems linked to low blood cell counts (like anemia or infections).

A stem cell transplant (SCT) lets doctors give higher doses of chemo, sometimes along with radiation therapy, to kill the cells in the bone marrow (including leukemia cells). After these treatments, the patient gets a transplant of blood-forming stem cells to restore their bone marrow.

Blood-forming stem cells used for a transplant come either from the blood (for a peripheral blood stem cell transplant, or PBSCT), from the bone marrow (for a bone marrow transplant, or BMT), or from umbilical cord blood. Bone marrow transplant was common in the past, but today it has largely been replaced by PBSCT.

When is a stem cell transplant used for chronic lymphocytic leukemia (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 a SCT might be considered include:

• To treat CLL that comes back after treatment or that's 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 (SCT)

The main types of stem cell transplants are:

Allogeneic SCT

In an allogeneic transplant, the stem cells come from someone else (a donor). To lower the chance of serious health problems, the donor needs to match the patient in terms of tissue type. Often, a close relative, like a brother or sister is 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 in people who are older or have other health problems.

Non-myeloablative transplant (mini-transplant): For people who are older or who have other health issues and can’t tolerate a standard allogeneic transplant that uses high doses of chemo, a non-myeloablative transplant (also known as a mini-transplant or reduced-intensity transplant) might still be an option. For this type of transplant, a person gets lower doses of chemo and radiation that don’t completely destroy the cells in their bone marrow. They then get the allogeneic (donor) stem cells. These cells enter the body and establish a new immune system, which sees the leukemia cells as foreign and attacks them (a graft-versus-leukemia effect).

This is the most common type of SCT used to treat CLL.

Autologous SCT

For an autologous transplant, the person’s own stem cells are collected from their blood or bone marrow before treatment. They are frozen and stored while the person gets treatment (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 the patient’s blood after treatment. One problem with this type of SCT is that there might be remaining leukemia cells that might be given back to the person along with the stem cells.

This type of SCT is rarely used to treat CLL.