Hematopoietic Stem Cell Transplantation, known as HSCT, offers an intensive treatment pathway for certain individuals living with multiple sclerosis. This medical procedure aims to reset the immune system, which in MS mistakenly attacks the body’s own central nervous system. The goal of this treatment is to halt the inflammatory processes that drive disease activity, rather than to repair existing neurological damage.
The Transplant Procedure Explained
The HSCT process for multiple sclerosis involves several distinct phases, utilizing the patient’s own stem cells in what is known as an autologous transplant. The initial step is stem cell mobilization and collection. Patients receive medications, such as granulocyte colony-stimulating factor (G-CSF) or low-dose chemotherapy, to stimulate their bone marrow to release hematopoietic stem cells into the bloodstream.
These stem cells, capable of forming all types of blood and immune cells, are then collected through apheresis. During apheresis, blood is drawn from a vein, passed through a machine that separates the stem cells, and the remaining blood is returned to the patient. This collection takes several hours over one to three days. The harvested stem cells are then frozen and stored until needed for the transplant.
Following collection, the patient undergoes a conditioning regimen, which involves high-dose chemotherapy. This phase aims to eliminate the existing immune system, including the self-reactive immune cells that contribute to MS activity. Common chemotherapy agents used include cyclophosphamide, sometimes combined with an immunosuppressive drug like anti-thymocyte globulin (ATG). This intensive treatment lasts several days, preparing the body for the new immune system.
After the conditioning treatment, the stored stem cells are thawed and infused back into the patient’s bloodstream through an intravenous drip. This day is referred to as “Day Zero” of the transplant. The infused stem cells naturally travel to the bone marrow, where they begin the process of engraftment.
Engraftment is the period when the newly infused stem cells settle in the bone marrow and start producing new, healthy blood and immune cells. This process takes about two to four weeks for white blood cell recovery, though a fully functional adaptive immune system can take months or even years to rebuild. During this time, patients are closely monitored as their immune system rebuilds.
Determining Candidacy for Treatment
Deciding who might benefit from HSCT for multiple sclerosis involves careful evaluation of individual patient characteristics and disease activity. This treatment is considered for individuals with highly active relapsing-remitting MS (RRMS) who have not responded adequately to other high-efficacy disease-modifying therapies (DMTs). This means they continue to experience frequent relapses or show new or active lesions on MRI scans despite conventional treatments.
Patient age is a factor, with younger individuals often being better candidates due to better recovery outcomes. Most studies focus on patients under 50 years old, though some centers consider individuals up to 70 years of age. Overall health is also assessed to ensure the patient can tolerate the intensive nature of the procedure, including evaluation of cardiac, lung, and kidney function.
The level of disability, often measured by the Expanded Disability Status Scale (EDSS), also plays a role. While HSCT is primarily for inflammatory MS, it may be considered for patients with active secondary progressive MS (SPMS) if there is ongoing inflammation or recent relapses. However, it is less commonly offered for advanced progressive forms of MS without active inflammation, as the stem cells cannot repair pre-existing nerve damage.
Efficacy and Therapeutic Goals
The primary goal of hematopoietic stem cell transplantation for multiple sclerosis is to halt disease progression and suppress inflammatory activity. The treatment aims to achieve “No Evidence of Disease Activity” (NEDA), which is a comprehensive measure indicating the absence of relapses, no worsening of disability, and no new or enlarging lesions on MRI scans. This outcome signifies control over the disease’s inflammatory component.
Clinical studies have reported high rates of NEDA following HSCT, particularly in patients with active relapsing-remitting MS. Some observational studies show NEDA rates ranging from 70% to 90%. A randomized controlled trial found that 99% of HSCT-treated individuals had no relapses for one year, and 94% did not experience disability worsening for three years, compared to those on other disease-modifying therapies.
While the main objective is disease stabilization, some patients may experience an improvement in their existing disability levels. Studies have noted improvements in EDSS scores for some individuals after HSCT. However, this is not the primary aim of the treatment, nor is it a guaranteed outcome for all patients. The procedure resets the immune system, preventing further autoimmune attacks.
Recovery and Potential Complications
The recovery period following hematopoietic stem cell transplantation is an intensive phase requiring careful medical management. Patients remain in the hospital for several weeks, sometimes in isolation, while their immune system rebuilds. This isolation period, known as the neutropenic phase, is when blood cell counts are very low, making the patient highly susceptible to infections.
During this time, patients receive supportive care, including antibiotics to prevent and treat infections, and may require blood transfusions. Common short-term side effects from the high-dose chemotherapy include nausea, vomiting, fatigue, hair loss, and mouth sores. These effects are temporary as the new immune system begins to engraft.
Beyond the immediate recovery, long-term risks are associated with HSCT. The intensive nature of the treatment carries a risk of treatment-related mortality, which has decreased over time to around 0.3% in studies after 2005. There is also a risk of developing secondary autoimmune diseases, although the incidence is reported to be lower than with some other MS therapies. Furthermore, the chemotherapy can impact fertility, causing permanent infertility or early menopause for women. Patients considering this treatment discuss options for fertility preservation, such as egg or sperm freezing, before the procedure.