The association between hospital volume and overall survival in adult AML patients treated with intensive chemotherapy

Abstract

Background: Acute myeloid leukemia (AML) requires specialized care, particularly when administrating intensive remission induction chemotherapy (ICT). High-volume hospitals are presumed more adept at delivering this complex treatment, resulting in better overall survival (OS) rates. Despite its potential implications for quality improvement, research on the volume-outcome relationship in ICT administration for AML is scarce. This nationwide, population-based study in the Netherlands explored the volume-outcome relationship in AML.

Materials and methods: Data from the Netherlands Cancer Registry on adult (≥18 years of age) ICT-treated AML patients, diagnosed between 2014 and 2018, were analyzed. Hospital volume was assessed against OS using mixed-effects Cox regression, adjusting for patient and disease characteristics (i.e. case mix), with hospital as a random effect.

Results: Our study population consisted of a total of 1761 patients (57% male), with a median age of 61 years. The average annual number of ICT-treated patients varied across the 24 hospitals (range 1-56, median 13, and interquartile range 8-20 patients per hospital per year). Overall, an increase of 10 ICT-treated patients annually was associated with an 8% lower mortality risk [hazard ratio (HR) 0.92, 95% confidence interval (CI) 0.87-0.98, P = 0.01]. This association was not significant at 30-day (HR 1.02, 95% CI 0.89-1.17, P = 0.75) and 42-day (HR 0.96, 95% CI 0.85-1.08, P = 0.54) OS but became apparent after 100-day OS (HR 0.91, 95% CI 0.83-0.99, P = 0.05).

Conclusions: There is a volume-outcome association within AML care. This finding could support hospital volume as a metric in AML care. However, it should be acknowledged that centralizing care is a complex process with implications for health care providers and patients. Therefore, any move toward centralization must be judiciously balanced.

Keywords: acute myeloid leukemia; population-based; quality of care; volume–outcome association.

Figure 1

Overall survival of patients with AML treated with ICT in the Netherlands. This figure shows the Kaplan–Meier curve for all AML patients treated with ICT in the Netherlands between 2014 and 2018. AML, acute myeloid leukemia; ICT, intensive remission induction chemotherapy.

Figure 2

Funnel plot for 1-year mortality following treatment with intensive chemotherapy. This funnel plot shows each hospital for each treatment year according to hospital volume on the x-axis and the ratio of observed-to-expected 1-year overall survival (O/E) on the y-axis. The expected mortality is determined using Cox regression analyses and adjusted for case-mix variables (i.e. age, sex, socioeconomic status, secondary AML, hyperleukocytosis, and ELN 2010 risk classification). The horizontal solid line represents the value wherein the observed cases equal the expected cases. The dashed lines represent the unadjusted 95% control limits, and Bonferroni corrected control limit. The effective sample does not correspond with the hospital volume since it is defined as the hospital volume adjusted for case mix and hospital follow-up. AML, acute myeloid leukemia; ELN, European LeukemiaNet.