Comparison of Survival Rates, Healthcare Resource Use and Costs of Elderly Patients with Chronic Myeloid Leukemia Receiving Dasatinib or Nilotinib As Second-Line Therapy

Introduction: Dasatinib and nilotinib are two second-generation tyrosine kinase inhibitors (TKIs) that are well established as treatment options for patients with Philadelphia chromosome positive chronic myeloid leukemia (Ph+ CML) in chronic phase resistant or intolerant to imatinib and the treatment guidelines do not differentiate based on patient age. Importantly, elderly patients (≥65 years old) account for about half of CML patients; yet there are little data reported focusing on outcomes in this distinct group of patients, often with multiple medical problems and different socio-economic profiles when compared to younger patients. This study aimed to compare survival rates, healthcare resource utilization (HRU), and medical service costs between elderly CML patients receiving dasatinib versus nilotinib as second-line therapy after imatinib.

Methods: Patients aged ≥65 years with ≥2 CML diagnoses who received imatinib as first-line therapy followed by nilotinib or dasatinib as second-line therapy were identified using the Medicare Research Identifiable Files (RIF) from 2006 to 2012. Selected patients were continuously enrolled in the Part A (i.e., institutional claims), Part B (i.e., non-institutional claims), and Part D (i.e., drug events) for ≥6 months before and ≥1 month after the second-line TKI therapy initiation date (i.e., index date). Patients enrolled in a clinical trial, those with a stem-cell transplant, or receiving chemotherapy (except hydroxyurea) during the 6 months before the index date (i.e., baseline period) were excluded from the study. Based on the second-line TKI, patients were classified as nilotinib users or dasatinib users. Survival rates were estimated using Kaplan Meir analyses and compared between nilotinib and dasatinib users using Cox proportional-hazards models. HRU and healthcare costs (USD 2013; payer’s perspective) were observed from the index date up to the end of follow-up. Because the length of follow-up varied across patients, HRU and costs were reported per-patient-per-month (PPPM). Incidence rate ratios (IRR) were estimated using Poisson regression models and monthly cost differences were estimated using general linear models with a log link and a gamma distribution or two-part models. Multivariate regression analyses were used to adjust for potential confounding factors measured during the baseline period or at the index date.

Results: After applying the sample selection criteria, 659 patients using a second-line TKI therapy were selected; 280 were nilotinib users and 379 were dasatinib users. On average, patients had a follow-up of 24 months (median=22 months) after the index date. The mean age was 76 years and most patients were female (62%). Nilotinib and dasatinib users were generally similar in terms of gender, region of residence, prior imatinib treatment duration, CML complexity, and comorbidity profile. However, nilotinib users were slightly older than dasatinib users; a greater proportion of nilotinib users were 80+ years old at the index date (35% of nilotinib users vs. 27% of dasatinib users; p=.039). In addition, the proportion of patients with cardiovascular disease (40% of nilotinib users vs. 31% of dasatinib users; p=0.015) or congestive heart failure (23% of nilotinib users vs. 14% of dasatinib users; p=0.002) during the baseline period was higher in nilotinib users when compared to dasatinib users. Despite these differences, the median survival time was >4.9 years for nilotinib users and 4.0 years for dasatinib users (log rank test p=.032). After adjusting for potential confounding factors, nilotinib users had a mortality risk that was 38% lower than that of dasatinib users (p=.006) and, nilotinib users had 21% fewer inpatient admissions, 17% fewer inpatient days, 31% fewer emergency room visits, and 12% fewer outpatient visits when compared to dasatinib users (PPPM; all p≤.001). The adjusted monthly medical cost was $378 lower in nilotinib users when compared to dasatinib users (PPPM; p=.045).

Conclusion: This retrospective study of elderly Medicare beneficiaries with CML receiving second-line therapy with dasatinib or nilotinib suggested that those receiving nilotinib had longer survival, lower HRU, and lower medical costs than those receiving dasatinib. Further health outcome researches and longer term studies focusing on elderly CML are needed to better define the best practice patterns.