Limitations to Receiving Allogeneic Hematopoietic Cell Transplantation for Treatment of Acute Myeloid Leukemia: A Large Multi-Center Prospective Longitudinal Observational Study

Introduction: Acute myeloid leukemia (AML) is most frequently diagnosed in older patients (pts), whose median survival is less than 1 year. Allogeneic hematopoietic cell transplantation (HCT) is a potentially curative treatment. However, older pts often have significant comorbidities and other geriatric health problems, and the effect of these on the probability of receiving HCT is unknown. To this end, we designed a prospective, multi-center, longitudinal, observational study dating from first presentation of adult pts with AML to be treated at one of 13 different referral centers that provide both AML treatment and HCT. We examined the effects of different variables (see methods) on the probability to 1) survive long enough to receive HCT and 2) to receive HCT if such survival occurred.

Methods: We enrolled 695 pts (Table 1). Data on demographics, AML status, cytogenetic risks per European Leukemia Network (ELN), and response; age; comorbidities per the HCT-comorbidity index (CI); function including instrumental activities of daily living (IADL) and activities of daily living (ADL); frailty including walk test; geriatric assessment (GA) including cognition; Karnofsky performance status (KPS); QOL including the Functional Assessment of Cancer Therapy-Bone Marrow Transplant Scale (FACT-BMT), Euro-QOL 5-Dimension scale (EQ-5D), ENRICHD Social Support Instrument, Social Activity Log, and Patient Health Questionnaire 9-item Depression Scale (PHQ-9) were collected at enrollment and at 1, 3, 6, 9, 12, 18, and 24 months thereafter. High-risk myelodysplastic syndromes (MDS) receiving AML-like therapy were included.

We used competing risk Cox regression analyses, treating HCT as the event of interest and death without HCT as a competing risk, with staggered entry (left truncation) at time of consent. Associations between variables were assessed both at enrollment and over time.

Results: The overall rate of HCT at 9 months after enrollment was 43% (Figure 1) and 92% of pts who received HCT did so by the 9 month mark.

In multivariate analyses, death without HCT (Table 2) was associated with augmented HCT-CI scores ≥5 (HR:2.11, p<0.0001), age ≥50 years with those aged ≥70 years having the highest association (HR:2.71, p<0.0001), ELN intermediate (HR:2.43, p=0.0003) or unfavorable risks (HR:4.3, p<0.0001), receiving low-intensity induction regimens (HR:1.42, p=0.04), relapsed/refractory disease at enrollment (HR:2.04, p<0.0001), dependent status per ADL scores <14 (HR:1.59, p=0.005), and depression per PHQ-9 (HR:1.56, p=0.009).

Among survivors (Table 3), low likelihood to receive HCT was associated with age ≥70 years (HR:0.40, p=0.0001), low ELN risk (HR:0.28, p<0.0001), low-intensity induction (HR:0.56, p=0.02), poor KPS (HR:0.49, p=0.0005), and relapse after initial complete remission (CR) (HR:0.41, p=0.001); while pts with high-risk MDS (HR:2.43, p<0.0001), relapsed/refractory disease at enrollment (HR:2.43, p<0.0001), and CR after induction (HR:4.59, p<0.0001) were more likely to receive HCT. Among pts aged ≥60 years, and after considering previous factors, impaired cognition (HR:0.45, p=0.007) and impaired hearing (HR:0.71, p=0.009) were associated with lower likelihood to receive HCT.

Conclusions: In a prospective, observational, multi-center study, increasing age, comorbidity burden, ELN risk, low-intensity initial AML induction regimen, depression, and functional dependence increase risks of early mortality without HCT.

In those who survived long enough to potentially receive HCT, age up to 69 years and/or multiple comorbidities were not found to be barriers to HCT, likely reflecting the widespread use of reduced-intensity conditioning regimens. However, the independent sharp decline in receipt of HCT in pts aged 70-80 years suggests continued bias, although pts in this age group have been shown to derive similar benefit from HCT as younger pts. Use of objective comorbidity and GA tools rather than age per se to decide on HCT is encouraged.

The adverse impact of impairments in psychological health and function on survival and of impairments of cognition, geriatric health, and performance status on receipt of HCT emphasize the need for interventions that target these health limitations in conjunction with AML treatment to improve outcomes.

Finally, the benefit of intensive vs. less-intensive induction therapies should be addressed with a randomized trial.

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