Stem cell transplants up, survival up: HHS study finds big gains for leukemia patients
But there’s plenty of room for improvement, especially among older patients
People with acute myeloid leukemia (AML) are living longer thanks to an increase in stem cell transplants from donors, a Hamilton Health Sciences (HHS) study has found. Findings were just published in Blood Cancer Journal.
AML is a rare and aggressive type of cancer that starts in the blood-forming cells of bone marrow. The best chance of a cure is an allogeneic (donor) transplant using healthy stem cells from a donor. Survival rates for AML patients have been steadily climbing over the last 15 years.
Transplant outcomes have improved over time, showing that not just more patients receive transplants, but that the patients who receive a transplant also have a higher chance for survival and cure.
The study was led by HHS hematologist and researcher Dr. Tobias Berg, and McMaster University leukemia and cellular therapy fellow Dr. Brittany Salter. It covered a 13-year span from 2010 to 2023 and reflects the current situation for AML patients and donor transplants in Ontario, says Berg, who leads research into AML at the Berg Research Lab at the Centre for Discovery in Cancer Research, where he is senior scientist and leads the translational oncology program. Berg is also a scientist with the Escarpment Cancer Research Institute (ECRI), a combined institute of HHS and McMaster. Berg cares for patients at the HHS Juravinski Hospital and Cancer Centre.
“While the use of allogeneic stem cell transplants has increased in recent years, this study is the first to look at how this trend affects patient outcomes,” says Berg.
The path to progress
The team analyzed health records of adult patients in Ontario diagnosed with AML between 2010 and 2023 to study their outcomes, using data from The Institute for Clinical Evaluative Sciences of Ontario (ICES), an independent, non-profit research organization.
AML samples from patients are stored in a special freezer at very low temperatures (-150 °C).
Statistical methods were used to look at how often stem cell transplants were done and how they affected patients’ chances of survival, while taking into account different factors like age, gender and overall health. The study also looked at timing, such as when patients received their transplant in relation to their diagnosis and treatment.
Of the 5,213 Ontario patients whose records were reviewed, 1,093 had been treated with a donor transplant. This amounted to about one in five patients, or 21 per cent.
The use of donor transplants to treat AML patients more than doubled, from 11.9 per cent in 2010 to 24.5 per cent in 2023, with the largest rise in the 40 to 59 year age group, the study found.
It also found that receiving a transplant is one of the most important factors associated with better survival. The median overall survival rate was 81 months, or almost seven years, meaning that half of transplant recipients lived even longer. For patients who didn’t qualify for a transplant and were treated with chemotherapy instead, the median overall survival rate was just 14 months, or a little over one year. Being aged 60 and older, being male, and having other health problems were linked to lower survival.
Who qualifies?
Overall health remains an important factor when deciding who’s eligible for a transplant, since patients need adequate heart, lung, liver, and kidney function to handle this treatment. Safer and less intensive transplant approaches have increasingly made transplantation feasible even for older and frailer patients. A suitable donor is also required, and patients must be able to stay near a transplant center and have a strong support system, since recovery involves careful monitoring, infection prevention, and frequent follow-ups.
Traditionally, younger adults ages 18 to 39 had the best shot of qualifying for a donor transplant because they tolerate intense treatments better and have a lower risk of serious complications. As people age, they can develop additional health problems that make transplants difficult to tolerate or survive. Their bone marrow and immune systems are often weaker, increasing the risk of infections and serious side effects from a transplant. Recovery is also slower with age, making complications more likely.
What the study found
Between 2010 and 2023, the percentage of 18 to 39-year-old AML patients receiving a donor transplant almost doubled, from about 37 per cent in 2010 to around 67 per cent in 2023. The study also found that patients not considered for transplant in this age group often have similarly good outcomes. These are often “good risk” patients who have genetic or chromosomal features that make AML more treatable and respond better to chemotherapy, with a higher chance of long-term survival.
AML cells under a microscope.
For patients aged 40 to 59, transplants more than doubled from about 21 per cent in 2010 to 53 per cent in 2023. For patients in their 60s, the percentage of transplants almost quadrupled over 13 years. Only 10 per cent of patients in this age group had a transplant in 2010, but by 2023 this number had climbed to 37 per cent. While these increases are worth celebrating, there remains important room for improvement and the need to remove barriers in these age groups, says Berg.
Research is the key to discovering new, better treatment options that are less toxic and invasive.
The news is much less promising for patients aged 70 and up. No one in this age group qualified for a transplant in 2010, and by 2023 just five per cent received a transplant. So this potential cure still isn’t an option for 95 per cent of patients 70 and older. Meanwhile, half of people diagnosed with AML are 69 years or older, so this patient group is in desperate need of safer, less invasive treatments and improved transplant strategies they can tolerate.
“Our findings sends a clear message that more research is needed into providing safe, manageable transplants to older adults,” says Berg. “In the higher age groups there’s still a lot of room to expand transplant.”
Research is the key to discovering new, better treatment options that are less toxic and invasive, adds Berg. “With new methodologies coming and better-tolerated transplant strategies, we’re hoping to expand even more to the older patient population.”
Reasons behind the rise
Over the past 20 years, Ontario has significantly increased investment in stem cell transplant programs to meet rising demand and improve patient care. These investments, including $25 million in provincial funding to JHCC to expand the transplant unit and oncology services, were driven by growing demand due to increasing blood cancer cases, an aging population, advances in transplant techniques, and a focus on equitable access to timely, high-quality care. The investments are also the result of important advocacy efforts, including the awareness sparked by Laura Hillier, an 18-year-old AML patient whose courageous public plea drew national attention to dangerous wait times for stem cell transplants. The Ron and Nancy Clark Stem Cell Transplantation and Cellular Therapies Unit at HHS was also made possible through $5 million raised by the HHS Foundation.
Improved donor matching and the use of alternative donors, in particular half-matched transplants, also helped expand the donor pool and improve survival for young and middle-aged adults. A half-match is usually a parent, child, or sibling.
The study has shown that expanding transplant access has also made transplants more equitable.
Advances in infection control; supportive care to manage symptoms, side effects, and complications; and improved management of graft-versus-host disease have further reduced complications and treatment-related death. These combined improvements have led to an increase in overall survival rates, which is another important finding of the study. Even as transplants have expanded to include more difficult-to-treat patients, outcomes have continued to improve. More people are receiving transplants, and those who do now have a higher chance of survival and cure.
Ensuring equity
The study has shown that expanding transplant access has also made transplants more equitable. However, there is still room for improvement to make transplants available to all patients in need, regardless of where they live in Canada, adds Berg. Health equity plays a vital role in helping ensure AML patients of all ages and backgrounds receive the best possible treatment. Expanding stem cell registries is a vital strategy in this context. The Canadian Blood Services Stem Cell Registry encourages people ages 17 to 35 to join, since donors in that age range give patients undergoing a stem cell transplant the best chance of long-term survival. Donors from diverse backgrounds are needed in order to save lives. Many people worldwide have difficulty finding a match due to a lack of diversity in stem cell registries.
Berg was the study’s principal investigator, interpreted results, and provided critical revisions and final editing of the manuscript; Salter developed grant and ethics applications, interpreted results and wrote manuscript; Alejandro Garcia-Horton, Irwin Walker, Kylie Lepic, Hira Mian assisted with protocol development and manuscript review; Gregory R. Pond, Hsien Seow and Anastasia Gayowsky performed data extraction and statistical analysis.
