Clinical Characteristics and Late-Line Treatment Patterns of Patients with Chronic Myeloid Leukemia Who Received 2 Prior Lines of Tyrosine Kinase Inhibitor Therapy in US Community Oncology Practices

BACKGROUND: Current treatment guidelines recommend tyrosine kinase inhibitors (TKIs) as first-line and second-line treatment options for patients with chronic myeloid leukemia (CML). ^1,2 However, approximately 20% of CML patients fail to respond to the first- and second-generation TKIs, and evidence-based guidelines for late-line treatment options after failure/intolerance to TKIs are limited. ^3,4 Therefore, this study sought to describe the clinical characteristics and real-world treatment patterns of CML patients who received 2 prior lines of TKI therapy.

METHODS: A retrospective cohort design was utilized to identify adult CML patients who initiated a new line of therapy (LOT) after 2 prior lines of TKI therapy between 4/2013 and 12/2020 in the Florida Cancer Specialists network's electronic health records (EHR) database. The index LOT date was the start date of a new CML treatment regimen in LOT≥3 after 2 prior lines of TKI therapy. Patients were followed until 1 of the following occurred: death, loss to follow-up (last structured activity in EHR), or end of study period (3/31/2021). Demographic and clinical characteristics were captured during the baseline period starting 3 months prior to the initial CML diagnosis until the index LOT date and included age, gender, race, Eastern Cooperative Oncology Group performance status (ECOG PS) and comorbidity burden. Treatment patterns of all available LOTs from initial CML diagnosis were investigated and the following metrics were captured: regimen details of systemic CML therapies, duration of LOT, treatment-free interval. This study was descriptive in nature and no inferential statistics were computed.

RESULTS: A total of 157 patients who initiated a new CML treatment regimen in LOT≥3 after 2 previous lines of TKI therapy were included in this study. The median age of the study sample at initial CML diagnosis was 63.8 years, 57.3% of the sample were male, and 50.3% were White. At index LOT, 46.5% of the sample had an ECOG PS score of 0-1, 5.1% had ECOG PS score of 2-4, and 48.4% had an unknown ECOG PS score. The majority of the sample initiated the index LOT in LOT 3 (n=151; 96.2%) vs in LOT 4 (n=6; 3.8%). The median duration of the index LOT was 6.6 months with median follow-up from index LOT being 23.0 months. After 2 prior lines of TKI therapy, 93.0% of the sample continued on TKIs only, 1.3% initiated a non-TKI CML drug, and 5.7% received a combination of CML drugs. Dasatinib (31.2%) and imatinib (30.6%) were the most commonly used TKIs in the index LOT. There was significant variability in the treatment sequences across LOTs, however, 50.3% of the sample restarted the same TKI in their index LOT which had been used in a prior LOT. A total of 65 patients (41.4%) initiated a new LOT after the index LOT, and the treatment-free interval following the index LOT was 1.8 months, on average.

CONCLUSIONS: The majority of the CML patients who received 2 prior lines of TKI therapy continue to cycle through additional LOTs containing TKIs, and half of the patients restart the same TKI used in a prior LOT. The findings of this study highlight the need for better novel therapies that can fill the treatment gap for CML patients who are refractory or intolerant to TKIs.

REFERENCES:

1. Deininger MW, Shah NP, Altman JK, et al. Chronic Myeloid Leukemia, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology. J Natl Compr Canc Netw. 2020;18(10):1385-1415.

2. Hochhaus A, Saussele S, Rosti G, et al. Chronic myeloid leukaemia: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2017;28(suppl 4):iv41-iv51.

3. Perrotti D, Jamieson C, Goldman J, et al. Chronic myeloid leukemia: mechanisms of blastic transformation. J Clin Invest. 2010;120(7):2254-2264.

4. Cortes J, Lang F. Third-line therapy for chronic myeloid leukemia: current status and future directions. J Hematol Oncol. 2021;14(1):44.