Stem cell transplantation can reduce disease activity for people with advanced systemic mastocytosis (SM) and may help patients live longer, according to a recent study published in the British Journal of Haematology.
Allogeneic stem cell transplantation replaces bone marrow that’s not producing enough healthy blood cells with new blood stem cells from a healthy donor. The authors noted that while stem cell transplantation has been used as a treatment, its efficacy and complications in advanced SM have not been extensively researched.
What is the difference between advanced and nonadvanced SM?
Nonadvanced SM comprises the indolent SM and smoldering SM subtypes. Advanced SM includes aggressive SM, SM with an associated hematologic neoplasm and mast cell leukemia.
The study looked at 27 adults with advanced SM who underwent allogeneic stem cell transplantation. On average, the number of mast cells in the bone marrow dropped from 15% before transplant to 1.5% one year later. Blood levels of tryptase, a protein that indicates immune cell activity (which is too high in SM), fell from 55 ng/mL to 18 ng/mL.
One year after transplant, 74% of patients were alive and 59% of patients were alive without the disease getting worse. Patients with a type of SM linked to another blood cancer (systemic mastocytosis with associated hematologic neoplasm, SM-AHN) had even better outcomes (with 79% alive overall and 74% alive without progression).
The chance of the disease returning was low, with 4% relapsing within 100 days and 15% within one year. In the SM-AHN group, relapse rates were slightly higher.
Read more about SM treatment and care
The researchers caution that the positive results might not be due to the transplant alone. Nearly nine out of 10 patients in the study had a mutation in the KIT gene, which drives the excessive production of mast cells in SM. Some patients received medicines called KIT inhibitors (such as midostaurin or avapritinib) either before or after the transplant, or even to treat relapse following transplant. These drugs specifically target the mutation that fuels the disease.
It’s hard to say exactly how much benefit comes from the stem cell transplant versus the KIT inhibitor medicines because this study included a relatively small number of patients, the researchers said. “In the near future, larger studies are required to provide further insights into this subject.”
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