
DNA from donor cells a key indicator of survival rates for transplant recipients
A Hamilton Health Sciences (HHS) study led by prominent hematologists at our Juravinski Hospital and Cancer Centre (JHCC) found that detecting ‘mixed chimerism’ in acute myeloid leukemia (AML) patients as early as one month after their donor stem cell transplant is linked to a higher risk of their cancer returning. This early detection could mean improved survival rates through early intervention and also supports a more personalized treatment approach for patients.
“This study supports HHS’s research vision for precision medicine, where leading-edge care and treatment are tailored to the patient’s individual needs.” — Dr. Marc Jeschke, HHS vice president of research and chief scientific officer
AML is an aggressive cancer that starts in blood stem cells, and is the most common type of acute leukemia in adults. While chemotherapy can knock AML into remission, the only potential cure in most cases is a stem cell transplant where donor stem cells are used to replace a patient’s diseased cells.
What is mixed chimerism?
Mixed chimerism is a condition where healthy donor stem cells don’t completely wipe out diseased cells after a donor stem cell transplant, so the patient has their own `old’ cells and donor-derived cells in their blood. These cells can be distinguished by their DNA. In a best-case scenario, the patient’s own DNA would not be detectable in their blood cells. Unlike blood donor recipients, stem cell transplant recipients will have the donor’s DNA in their blood cells for the rest of their lives, since stem cells are what produce new blood cells.
About 60 percent of AML patients who undergo a transplant will be cured, while the remaining 40 percent will eventually see their cancer return. Researchers believe more patients can be cured by identifying mixed chimerism early and intervening.
Partnering with HHS patients
The HHS study’s findings were recently published in the journal, Transplantation and Cellular Therapy. This research involved 141 patients from JHCC who received a donor stem cell transplant between 2016 and 2022 through the hospital’s Cellular Therapy and Transplant Program. The JHCC is one of only three full service complex malignant hematology centres in Ontario and a recognized clinical and research centre.
Study participants had been diagnosed with AML or myelodysplastic syndrome (MDS), a condition where the bone marrow doesn’t make enough healthy blood cells. MDS has a high risk of turning into AML.
“This study is an excellent example of how collaboration drives leading-edge research and precision medicine aimed at prolonging and saving lives.” — Dr. Tobias Berg, HHS hematologist
Chimerism, or mixed DNA, was measured in patients’ blood at 30, 60 and 90 days post transplant. Research partners included the Hamilton Regional Laboratory Medicine Program (HRMLP)’s genetics lab at JHCC.

This study involved close collaboration between partners including JHCC’s Cellular Therapy and Transplant program, the clinical genetics lab at the HRLMP and the Centre for Discovery in Cancer Research at McMaster University.
“Researchers looked at the genetic fingerprint of cells,” says Dr. Tobias Berg, an HHS hematologist and a study author. “If the genetic fingerprint, as early as 30 days after transplant is all from the donor, then the risk for leukemia returning is much lower, and the chance for the patient to be cured is a lot better. We can use this finding to provide more personalized care and are working on new strategies to improve the outcome of patients with a higher risk for relapse.”
Findings open the door for early intervention, by identifying chimerism as early as 30 days post-transplant. Early detection means doctors can take steps to wipe out any remaining diseased cells before they trigger a relapse. Interventions could include a donor lymphocyte infusion (DLI), where immune cells are collected from the original stem cell donor and used to boost the effect of the donor immune cells and eliminate the remaining diseased cells. Immune cells help the body fight diseases.
“With a DLI, it’s a fast, one-time collection and the recipient receives these cells in an easy outpatient procedure, so no overnight stay is required,” says Berg.
The study recommends more monitoring of chimerism over time for more accurate predictions. Further research could also help determine the best ways to treat mixed chimerism.
Research dream team
“This study supports HHS’s research vision for precision medicine, where leading-edge care and treatment are tailored to the patient’s individual needs,” says Dr. Marc Jeschke, vice president of research and chief scientific officer for HHS.
HHS is a top 10 Canadian research hospital, and the study is a close collaboration between the hospital’s Cellular Therapy and Transplant program, the clinical genetics lab at the HRLMP and the Centre for Discovery in Cancer Research at McMaster University, where Berg is senior scientist and leads the translational oncology program.
This program acts as a bridge between lab-based scientists and clinicians working to improve the lives of patients affected by cancer. Berg is also a scientist with the Escarpment Cancer Research Institute (ECRI), a joint institute of HHS and McMaster University. Based at JHCC, ECRI’s work focuses on research that has an impact on patient outcomes.
HHS hematologist Dr. Michael Radford, a specialist in allogenic stem cell transplants, was the study lead, backed by a team of heavy hitters that also included: Dr. Irwin Walker, a leader in hematology at JHCC and pioneer in the field of allogenic stem cell transplants; Dr. Brian Leber, who in 2019 made HHS history by performing the thousandth allogenic stem cell transplant at JHCC; Dr. Kylie Lepic, medical director of the HHS Cellular Therapy and Transplant Program; and Dr. Gregory Pond, a statistician and ECRI’s director. Other authors are Daria Grafodatskaya and Elizabeth McCready from the HRMLP; McMaster University’s Dr. Alejandro Garcia Horton, Dr. Dina Khalaf, Dr. Rohail Badami and Dr. Elaine Jin; and Dr. Nida Usmani from Montreal’s Charles-Bruneau Cancer Center.
“This study is an excellent example of how collaboration drives leading-edge research and precision medicine aimed at prolonging and saving lives,” says Berg, of these partnerships.