Photo by Chad McNeeley
SAN DIEGO—Researchers believe they have identified patients with chronic myeloid leukemia (CML) who are likely to derive long-term benefit from allogeneic hematopoietic stem cell transplant (allo-HSCT).
The researchers found that CML patients have a low risk of long-term morbidity if they undergo HSCT before the age of 45, are conditioned with busulfan and cyclophosphamide (Bu/Cy), and receive a graft from a matched, related donor (MRD).
Jessica Wu, of the University of Alabama at Birmingham, presented these findings at the 2016 ASH Annual Meeting (abstract 823*).
Wu noted that allogeneic HSCT is potentially curative for CML, but this method of treatment has been on the decline since the introduction of tyrosine kinase inhibitors (TKIs). And today, few CML patients undergo allo-HSCT.
She said that although TKIs can induce remission in CML patients, the drugs also fail to eradicate leukemia, can produce side effects that impact patients’ quality of life, and come with a significant financial burden (estimated at $92,000 to $138,000 per patient per year).
With this in mind, Wu and her colleagues set out to determine if certain CML patients might benefit from allo-HSCT long-term. The team also wanted to quantify overall and cause-specific late mortality after allo-HSCT and the long-term burden of severe/life-threatening chronic health conditions after allo-HSCT.
Patient population
The researchers studied 637 CML patients treated with allo-HSCT between 1981 and 2010 at City of Hope in Duarte, California, or the University of Minnesota in Minneapolis/Saint Paul. The patients had to have survived at least 2 years post-transplant.
About 60% of patients were male, and 67% were non-Hispanic white. Their median age at HSCT was 36.4 years, and 65% received an MRD graft. Nineteen percent of patients were transplanted in 1980-1989, 52% were transplanted in 1990-1999, and 29% were transplanted in 2000-2010.
Fifty-eight percent of patients received Cy/total body irradiation (TBI), 18% received Bu/Cy, and 3% received reduced-intensity conditioning (RIC).
Sixty-one percent of patients had chronic graft-vs-host disease (cGVHD), and 32% had high-risk disease at the time of HSCT.
Survival
The patients were followed for a median of 16.7 years. Thirty percent (n=192) died after surviving at least 2 years post-HSCT.
The median time to death was 8.3 years (range, 2-29.5), and the median age at death was 49.2 (range, 7.8-69.8). At 20 years from HSCT, the overall survival was 68.6%.
HSCT recipients had a 4.4-fold increased risk of death compared with the age-, sex-, and race-matched general population.
“Non-relapse mortality was the major contributor to late mortality, with infection, second malignancies, and cGVHD being the most common causes of death,” Wu said.
Non-relapse mortality was 20%, and relapse-related mortality was 4%. Eight percent of patients died of infection, 6.3% died of cGVHD, and 3.7% died of second malignancies.
Health outcomes
Patients who were still alive at the time of the study were asked to complete the BMTSS-2 health questionnaire, which was used to examine the risk of grade 3/4 chronic health conditions.
A total of 288 patients completed the questionnaire, as did a sibling comparison group of 404 individuals.
Among the patients, the median age at allo-HSCT was 37.5 (range, 3.6-71.4), and the median duration of follow-up was 13.9 years (range, 2-34.6).
Sixty-two percent of patients received an MRD graft, and 38% had a matched, unrelated donor. Eighty-three percent of patients had TBI-based conditioning, 16% received Bu/Cy, and 2.7% received RIC.
The prevalence of grade 3/4 chronic health conditions was significantly higher among patients than among siblings—38% and 24%, respectively (P<0.0001).
The odds ratio (OR)—adjusted for age, sex, race, and socioeconomic status—was 2.7 (P<0.0001).
The cumulative incidence of any grade 3/4 condition at 20 years after HSCT was 47.2% among patients. Common conditions were diabetes (14.9%), second malignancies (12.6%), and coronary artery disease (10%).
The researchers found the risk of grade 3/4 morbidity was significantly higher for the following patient groups:
- Those age 45 and older (hazard ratio [HR]=3.3, P<0.0001)
- Patients with a matched, unrelated donor (HR=3.0, P<0.0001)
- Those who received peripheral blood or cord blood grafts as opposed to bone marrow (HR=2.7, P=0.006).
(This analysis was adjusted for race/ethnicity, sex, education, household income, insurance, cGVHD, and conditioning regimen).
Lower risk
To identify subpopulations with a reduced risk of long-term morbidity, the researchers calculated the risk in various CML patient groups compared to siblings.
The overall OR for CML patients compared with siblings was 2.7 (P<0.0001).
The OR for patients in first chronic phase who underwent HSCT before the age of 45 and had an MRD was 1.5 (P=0.1).
The OR for CML patients in first chronic phase who underwent HSCT before the age of 45, had an MRD, and received Bu/Cy conditioning was 0.8 (P=0.7).
“[W]e found that patients who received a matched, related donor transplant under the age of 45, with busulfan/cyclophosphamide, carried the same burden of morbidity as the sibling cohort,” Wu said. “These findings could help inform decisions regarding therapeutic options for the management of CML.”
Wu noted that the limited sample size in this study prevented the researchers from examining outcomes with RIC. And a lack of data at analysis prevented them from examining pre-HSCT and post-HSCT management of CML, the interval between diagnosis and HSCT, and the life-long economic burden of allo-HSCT.
However, she said data collection is ongoing, and the researchers hope to address some of these limitations.
*Information presented at the meeting differs from the abstract.