Exclusion of Acute Myeloid Leukemia Patients with Central Nervous System Involvement from Clinical Trials: An Analysis of the National Institutes of Health Clinical Trials Registry from 2012 to 2022.

Introduction: Central nervous system (CNS) involvement in acute myeloid leukemia (AML) can be successfully treated with intrathecal chemotherapy and carries debatable prognostic impact. However, patients with CNS involvement are commonly excluded from clinical trials at an unknown rate. We systematically evaluated exclusion criteria of AML clinical trials based on CNS involvement and determined associations with clinical trial characteristics.

Methods: The National Institutes of Health Clinical Trials Registry was searched for interventional adult AML trials between 2012 and 2022 that were phase 1, 2, or 3 and relevant trial characteristics were extracted.

Results: 1,270 trials were included in the analysis with 790 trials (62.1%) explicitly excluding CNS involvement. There was no significant change in rates of CNS exclusion over the past decade. CNS exclusion was higher in trials that included the non-transplant population compared to trials exclusive to the transplant population (66.9% vs. 43.8%, p < 0.01). Non-transplant trials were also more likely to exclude patients with a history of or ambiguous timing of CNS involvement (p < 0.01). Phase 3 trials were associated with more liberal definitions of CNS exclusion (history or ambiguous timing) as compared to phase 1 and 2 trials that had higher rates of excluding patients with only active CNS involvement (p < 0.01).

Conclusion: A majority of AML clinical trials, particularly in the non-transplant setting, exclude patients with CNS involvement. Many of these trials, most notably phase 3 trials, exclude patients not only with active but also with any history of CNS involvement. Further research is needed to determine optimal management of these patients in order to increase representation in large clinical trials.