Myelodysplastic Syndromes (MDS) are cancers where the bone marrow fails to produce enough healthy, mature blood cells. Instead, it generates immature cells that do not function correctly, leading to low levels of red blood cells, white blood cells, and platelets. This can cause anemia, infections, or bleeding issues. An allogeneic stem cell transplant is an intensive treatment for MDS, aiming to replace these unhealthy cells with healthy ones.
The Goal of Transplant for MDS
The primary goal of an allogeneic stem cell transplant for MDS is to replace the patient’s diseased bone marrow with a healthy blood-forming system from a donor. This procedure is considered the only treatment with the potential to cure MDS, especially for those with higher-risk forms.
Another benefit is the “graft-versus-leukemia” (GVL) effect. This occurs when the donor’s immune cells recognize and target any remaining MDS cells in the patient’s body. These cells destroy the foreign MDS cells, helping to prevent disease recurrence.
Eligibility and Donor Selection
Patient suitability for a stem cell transplant is determined by age and overall health status, often assessed using performance status and comorbidity scales. While there is no strict age limit, healthier individuals generally tolerate the intensive treatment better.
Disease-specific factors, particularly the subtype of MDS and its risk score, are also considered. Transplants are typically for patients with higher-risk MDS. Lower-risk patients may be considered if they have poor genetic features, profound cytopenias, or a high transfusion burden.
Once eligible, a compatible stem cell donor is sought, focusing on Human Leukocyte Antigen (HLA) matching. HLA are proteins on cell surfaces that help the immune system distinguish between “self” and “non-self” cells, acting like a cellular fingerprint. A close HLA match is important to reduce complications like graft-versus-host disease and improve transplant success.
Donor sources include:
Matched related donors, usually siblings.
Matched unrelated donors (MUD) from national or international registries.
Haploidentical donors, who are half-matched family members.
Umbilical cord blood, which contains stem cells.
The Allogeneic Transplant Procedure
The transplant process begins with a conditioning regimen, preparing the patient’s body for new stem cells. This intensive treatment typically involves high-dose chemotherapy and sometimes radiation therapy. Its purpose is to eliminate the existing bone marrow and suppress the immune system to prevent rejection of donor cells.
Conditioning regimens are categorized into myeloablative (MAC) and reduced-intensity conditioning (RIC). Myeloablative regimens use very high doses designed to completely destroy the bone marrow. RIC regimens use lower doses that suppress the immune system and create space in the marrow. RIC is often considered for older patients or those with other health concerns.
On transplant day, the donor stem cells are infused into the patient, a process similar to a blood transfusion. The stem cells are delivered intravenously, flowing from a bag through a central line, and typically takes one to several hours. This infusion is not a surgical procedure.
After infusion, engraftment begins as new stem cells travel to the bone marrow and start producing healthy blood cells. This process typically takes two to six weeks, with white blood cells often being the first to show signs of recovery. During this time, patients are closely monitored with daily blood counts and receive supportive care, including transfusions and antibiotics.
Navigating Recovery and Potential Complications
After engraftment, the patient’s new immune system rebuilds, a process that can take many months to over a year. During this time, patients are susceptible to infections. They must take prophylactic medications to prevent bacterial, viral, and fungal infections, especially in the first 100 days post-transplant.
A potential complication following an allogeneic transplant is graft-versus-host disease (GVHD). This occurs when the donor’s immune cells recognize the patient’s tissues as foreign and attack them. GVHD can manifest in two main forms: acute and chronic.
Acute GVHD typically develops within the first 100 days after transplant and commonly affects the skin, liver, and gastrointestinal tract. Symptoms might include a rash, nausea, vomiting, diarrhea, or elevated liver enzymes. Chronic GVHD usually appears more than 100 days post-transplant and can affect a wider range of organs, including the skin, mouth, eyes, lungs, and joints. Both acute and chronic GVHD are managed with immunosuppressive medications.
Long-term follow-up care involves regular visits to the transplant center for monitoring. This includes blood tests to assess blood counts and immune function, and screening for complications or disease recurrence.