New tools predict stem cell transplant risks in myelofibrosis

An international team of researchers has developed a new score to predict the risk of disease recurrence after stem cell transplant in people with myelofibrosis, along with a separate score to predict non-relapse mortality (death in the absence of myelofibrosis recurrence).

The relapse risk score is based mainly on genetic abnormalities found in the abnormal blood cells of myelofibrosis, while the mortality score is based on clinical variables such as age and co-occurring health problems. The two scores have little overlap, suggesting that the factors driving relapse and non-relapse mortality are distinct in myelofibrosis patients undergoing stem cell transplant.

“Relapse and nonrelapse mortality after [stem cell] transplantation for myelofibrosis are determined by different and largely nonoverlapping variables,” the researchers wrote. “Estimating both separately, rather than only the composite of survival, identifies which of the two accounts for an individual patient’s risk.”

The information “may help transplantation optimization as well as weigh transplantation against other therapies,” they said.

The study, “iMTSS: an integrated framework for biology- and patient-driven prognosis in myelofibrosis undergoing transplantation,” was published in Transplantation and Cellular Therapy.

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Myelofibrosis is caused by the abnormal production of blood cells. Blood cells are produced by specialized stem cells in the bone marrow. An allogeneic stem cell transplant (also called a bone marrow transplant) involves replacing these blood-producing stem cells with stem cells from a donor.

Stem cell transplant is the only intervention that can cure myelofibrosis. However, the procedure is not always successful. Conceptually, there are two main ways that a stem cell transplant can fail: relapse, where the disease comes back after the transplant, and non-relapse mortality, where patients die due to complications unrelated to myelofibrosis. The researchers wanted to better understand what drives each of these outcomes.

The scientists analyzed data from 1,550 people with myelofibrosis who underwent stem cell transplantation at centers in Europe and the U.S. Most patients were followed for more than five years after transplant.

At five years post-transplant, the overall survival rate was 61%. Rates of relapse and non-relapse mortality at five years were 18% and 30%, respectively.

The researchers used detailed statistical models to look for factors at the time of transplant that significantly predicted the long-term risk of relapse or non-relapse mortality.

In the resulting models, relapse risk was largely governed by disease-specific factors, such as whether abnormal blood cells carried mutations affecting TP53 (a protein that regulates cell growth and is often mutated in cancers). Mutations in other cancer-related genes, such as ASXL1 and the RAS pathway, were also associated with relapse risk.

The risk of non-relapse mortality, on the other hand, was hardly affected at all by disease-intrinsic factors. Instead, the researchers’ model suggested that non-relapse mortality risk is affected mainly by a person’s underlying health status and factors related to the transplant procedure. Specific factors associated with non-relapse mortality in the model included age, donor type, patients’ functional status, and portal vein thrombosis (clots in a large blood vessel in the liver).

Based on these two models, the researchers developed an online tool called iMTSS to calculate the risk of relapse and non-relapse mortality in patients with myelofibrosis.

“Rather than returning a single risk number, iMTSS indicates why a given patient is at risk,” which may be useful for guiding individual treatment decisions in future clinical trials, they wrote.