Bone marrow, the spongy tissue inside our bones, is the factory for blood cells. It creates hematopoietic stem cells that transform into several cell types, including:
red blood cells, which carry oxygen to our tissues
platelets, which stop bleeding
white blood cells, which fight infection
Blood cancers multiply uncontrollably, hindering the growth of these cells. A hematopoietic stem cell transplant replaces faulty cells so the body can produce normal, healthy cells again.
What are the types of stem cell transplants?
Stem cell transplants fall into two categories: autologous and allogeneic.
An autologous stem cell transplant uses the patient’s own cells for treatment. We extract blood cells, treat the cancer with high-dose chemotherapy, then place the cells back into the patient. The patient has low blood counts until the replaced cells replenish the patient’s body with healthy cells.
An allogeneic stem cell transplant is similar, but we take cells from someone other than the patient. The transplanted cells kill any remaining cancer cells and restore the patient’s immune system.
Where do allogeneic stem cell transplant donor cells come from?
There are three types of allogeneic stem cell transplants:
bone marrow transplants
peripheral blood transplants
cord blood transplants
With a bone marrow transplant, the donor receives general anesthesia, and the bone marrow is extracted in a 1-2-hour procedure. Once the cancer is less active and the patient has been pre-treated with chemotherapy (known as conditioning), he or she receives the donor’s healthy stem cells.
With a peripheral blood cell transplant, the donor receives growth factor shots to stimulate the bone marrow to push the stem cells into the blood. This allows us to collect more cells in a short period, decrease patient/donor downtime and freeze the cells for future use.
The cells for a cord blood transplant come from an umbilical cord collected at birth by the MD Anderson Cord Blood Bank. For many patients who don’t have a well-matched, healthy donor, a cord blood transplant is a viable option.
What determines if a donor is a good match?
We all have protein structures called human leukocyte antigens (HLA) on our cells’ surfaces. We try to find a donor who has 10 antigens that match 10 of the patient’s antigens. Since antigens are inherited, family members, specifically siblings, are a good starting point, but a family match isn’t guaranteed. Many patients find matched unrelated donors through the National Marrow Donor Program.
The closer the match, the less risky the transplant. If the donor cells aren’t a close enough match, the patient’s body may recognize the donor cells as foreign and reject them. Or, the cells from the donor may recognize the new body as foreign and attack. This is called graft-versus-host disease.
If the patient can’t find a family or unrelated donor, it’s possible to have a successful transplant with a partially matched related donor, known as a haploidentical stem cell transplant.
How do you decide what type of stem cell transplant a patient receives?
We consider the type of disease and its progression. Most patients with multiple myeloma or lymphoma receive autologous transplants; most leukemia patients receive allogeneic transplants.
Other factors we consider include:
availability of a suitable donor
age and health of the patient and donor
Can a stem cell transplant be used in combination with other cancer treatments?
The transplant has three phases. A week prior to the transplant, the patient is conditioned with high-dose chemotherapy to destroy most of the cancer and the patient’s defective immune system. Then, the transplant repopulates the immune system with the healthy cells.
Based upon how a patient responds, the patient may receive more treatment in a third phase. MD Anderson has had success using post-transplant maintenance therapy with low-dose therapy with chemotherapy and/or immune-stimulating drugs. We’re now exploring adding engineered T-lymphocytes and/or engineered natural killer cells to strengthen the immune system after the transplant in patients at high risk for infection or recurrence.
Tell us about new stem cell transplant research at MD Anderson.
MD Anderson has the largest stem cell transplant operation in the world. Our research aims to speed up patients’ recovery and lower risk of complications.
For example, our research in the conditioning process has improved autologous transplants for advanced Hodgkin’s disease and large cell lymphoma. We’ve also developed a practice-changing approach for conditioning patients with acute leukemia. In addition, we’re working to improve and expand cord blood transplants. And we’re studying prevention and treatment of immune-related complications, such as graft-vs-host disease, after allogeneic stem cell transplantation.
We’re also exploring the use of cellular therapy to treat advanced blood cancers, solid tumors, organ failure, and autoimmune and genetic diseases.
What’s your advice for potential stem cell transplant patients?
Research and learn as much as you can before seeing your doctor. Meet with a transplant specialist, and come prepared with questions. Consider all available options, and don’t be afraid to seek a second opinion.
Your support system is integral your success. Bring someone with you to your consultations to take notes and process the information. Sometimes you’ll depend solely on your caregiver.
There’s never a “right” treatment decision. So, it’s important to work with your doctor and carefully choose the option that optimizes your chances for a successful recovery and best fits your life.