Comprehensive Survival Analysis of Alveolar Echinococcosis Patients, University Hospital Zurich, Zurich, Switzerland, 1973-2022

Abstract

Alveolar echinococcosis (AE) is a zoonotic disease of increasing concern worldwide. Before benzimidazole drug therapy, 10-year death rates were 90% without surgical resection. In unresectable patients, long-term benzimidazole therapy is highly effective in stabilizing the disease course. We performed a retrospective study of 334 AE patients treated at the University Hospital Zurich, Zurich, Switzerland, during 1973-2022. Annual diagnoses increased over time, and more cases were detected by chance at earlier stages. Ninety patients died, mostly from causes unrelated to AE. Relative survival of AE patients compared with the population of Switzerland demonstrated a steady decrease 5 years after diagnosis. Patient age at diagnosis was the primary variable associated with overall survival. In a propensity-score matched survival analysis, early curative surgery was associated with overall improvement but not AE-specific survival. We conclude that survival of patients with AE is limited by non-AE causes and that early curative surgery does not improve AE-specific survival.

Keywords: Alveolar echinococcosis; Echinococcus multilocularis; Switzerland,; Zurich; albendazole; benzimidazole; mebendazole; mortality; parasites; relative survival; resection; surgery; survival.

Figure 1

Total number of new, symptomatic, and incidental AE diagnosis by calendar year, University Hospital Zurich, Zurich, Switzerland, 1973–2022. AE, alveolar echinococcosis.

Figure 2

Stages and treatment of AE cases by decade, University Hospital Zurich, Zurich, Switzerland, 1973–2022. A) AE stages; B) treatment strategies. Although palliative surgery was discontinued in the early 2000s, curative surgery was less frequently pursued in the last decade of the study period. AE, alveolar echinococcosis; BMZ, benzimidazole drug therapy.

Figure 3

AE and non-AE associated causes of death for AE patients, by decade of AE diagnosis, University Hospital Zurich, Zurich, Switzerland, 1973–2022. AE associated death was observed more frequently in earlier decades of the study period. AE, alveolar echinococcosis.

Figure 4

Causes of death other than alveolar echinococcosis in alveolar echinococcosis cases, University Hospital Zurich, Zurich, Switzerland, 1973–2022.

Figure 5

Relative survival analysis of alveolar echinococcosis cases, University Hospital Zurich, Zurich, Switzerland, 1973–2022. A) Relative survival of alveolar echinococcosis patients compared with the population of Switzerland. B) Relative survival grouped by age at alveolar echinococcosis diagnosis. One patient with an alveolar echinococcosis diagnosis at 86 years of age and died at age 99 was excluded for better visualization (Appendix Figure 2).

Figure 6

Matched survival analysis of AE cases, University Hospital Zurich, Zurich, Switzerland, 1973–2022. A) Results of nearest neighbor matching. Non-AE death hazard ratio (HR) = 0.48 (95% CI 0.30–0.77), p = 0.002; AE death HR = 0.15 (95% CI 0.02–1.27), p = 0.082. B) Results after genetic matching. Non-AE death HR = 0.49 (95% CI 0.29–0.84), p = 0.009; AE death HR = 0.18 (95% CI 0.02–1.56), p = 0.12. Patients undergoing curatively intended surgery within 1 year of diagnosis showed better overall survival. AE-related death did not differ after matching. AE, alveolar echinococcosis.