Will I Need a Stem Cell Transplant for CML and How Do I Find a Match?

In CML, a stem cell transplant may be used if a patient stops responding to treatment with a type of targeted therapy called a tyrosine kinase inhibitor (TKI) or has a relapse. A relapse is the recurrence of the cancer.

"The concept behind the stem cell transplant is that we are giving patients a new immune system so we can wipe out leukemia but give them basically a new bone marrow system so that they can make their red cells and white cells and platelets," Dr. Eric Winer, Director of the Adult Leukemia Institute at Dana-Farber Cancer Institute, tells SurvivorNet.

"But because it’s a different immune system, that immune system is going to recognize the old leukemia cells as foreign," Dr. Winer explains.

"They are going to target those leukemia cells and pull them out of circulation. Thus, it acts as this sort of continuous surveillance that we don’t see in the patient taking the TKI.”

When is a Stem Cell Transplant Needed?

Because TKIs work so well in treating CML, stem cell transplants are now used rather infrequently nowadays. However, they can still work very well in certain patients.

"What’s interesting and helpful for CML is that we don’t use transplant nearly as often as we used to before we had TKIs,” Dr. Winer says. "… We don’t use it very often for the simple reason that the TKI works so well."

Stem cell transplant from a donor is considered for patients who have resistance to at least two types of TKIs: if they are in the advanced phase of CML (accelerated or blast phase), or intolerant to multiple TKIs.

"Stem cell transplant is still an option for this minority of patients that really transform to advanced phases of these conditions,” Dr. Javier Pinilla, head of the Lymphoma Section at Moffitt Cancer Center, tells SurvivorNet.

Is a Stem Cell Transplant Right for You?

"If the patients are not having a good response to the TKI, then we talk about bone marrow transplant,” Dr. Winer explains. "Oftentimes, with accelerated phase and the blast crisis group, we treat more aggressively and then we move towards an allogeneic bone marrow transplant."

The decision to pursue stem cell transplantation has become more challenging because many patients have remarkable responses to TKIs for very long periods and preserve their quality of life without the serious risks of transplantation. On the other hand, side effects are common, and resistance may develop with TKI.

It is normal to feel overwhelmed or anxious when you find out that you need a stem cell transplant. Your doctor will consider several important factors when making the decision.

These factors include:

•  Age
• Overall health
•  Phase of CML
• Response to TKI
• Availability of a well-matched donor

Your doctor, who is familiar with the details of your diagnosis, can give you more information about whether a stem cell transplant is an option for you.

What's the Data on Stem Cell Transplants?

Patients with CML who do not respond well to TKIs may progress to a more aggressive phase of CML. Stem cell transplant from a matched sibling or unrelated donor has shown incredible promise during the last decade in CML. Updates from the American Society of Hematology (ASH) 2022 presented real-life data on outcomes after stem cell transplantation. About 70 to 90 percent of the patients with CML who undergo stem cell transplantation from donors are cured of their CML. These patients remained disease-free after five years.

What are the Risks?

There are numerous risks involved in a stem cell transplant from a donor. Whether or not you'll experience significant side effects from transplant depends on several factors, including phases of CML (chronic, accelerated, or blast), donor (related and unrelated), and biological sex differences. The mortality rate remains high, and approximately 20%-25% of patients who undergo stem cell transplantation may die from the complications of the procedure. Those who are cured may also develop chronic side effects from the transplant.

Possible complications from a stem cell transplant include:

• Graft-versus-host disease (when donor cells attack the recipient’s)
• Stem cell (graft) failure
• Organ damage
• Infections
• New cancers
• Death

How Are Donors for Stem Cell Transplantations Found?

That donor could be:

• A sibling
• An unrelated individual that's a tissue match
• A baby's cord blood
• A half-matched person

One of the first steps to consider when searching for a donor is to find out whether a family member is a suitable match. The process involves running special blood studies such as tissue typing, and high-resolution DNA typing on you and your entire family.

Dr. Costello board-certified hematologist at UC San Diego Health, explained to SurvivorNet previously that, "The ideal donor for an allogeneic stem cell transplant is someone who has more or less … identical genes to you."

"We're talking about your major genetic makeup," she explains. "Mom and dad each gave you five different genes, that is your DNA, your genetic makeup, your blueprint."

Siblings have a 1 in 4 chance of matching. A close relative may also be a potential match.  The remaining patients need to find an unrelated donor whose stem cell is compatible.

What is the Process For Finding a Stem Cell Match?

For CML patients without a family match, a search for an unrelated donor is performed through a registry known as the National Marrow Donor Program (NMDP)/Be The Match Registry.  Currently, there are nearly 39 million volunteer donors in the National Marrow Donor Program (NMDP). The likelihood of patients searching the NMDP having at least one identically matched, the unrelated donor is ranging from 29%-79%. Depending on the search results, your transplant team will discuss the next steps with you.

"CML patients who are diagnosed in the blast phase need to start the workup for an allogeneic bone marrow transplant. Ideally for an HLA match, for a match-related donor for someone who’s related in the genes. But if not available, there are many other opportunities like an international bone marrow registry or even other relatives that also be able to donate the bone marrow," Dr. Pinilla explains.

What is a Half-Matched Donor?

A haploidentical donor, or simply a half-matched donor can also be selected as an alternative donor if no matched donor is available. Biologic parents are almost always half-matched, or haploidentical for their children.

According to Dr. Winer, "It means that you don’t have to have a full match in terms of the chromosomes. You can have a half match, meaning matching only one parent, but more importantly, it means matching a child. So, children can donate to their parents because they have half of the same DNA as their parents,” he explains.

"That allows the database to be much broader in terms of who can be a potential donor. So, we think about the siblings first, and then we think about the database, and then we move towards half matches, which could be children, it could be siblings in some circumstances we’ve even seen it with nieces and nephews."

Questions to Ask Your Health Care Team

• What side effects of stem cell transplant should I be aware of?
• Which is better for me, a matched donor from the National Marrow Donor Program (NMDP) or a family member?
• Will I need additional treatment before or after the transplant?
• Are there other treatment options I should consider?
• How will the transplant change my normal activities?
• What follow-up care will be needed after the transplant is complete?

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