Comprehensive Diagnosis and Treatment of Alveolar Echinococcosis : A Single-center, Longterm Observational Study of 312 Patients in Germany

All patients with Alveolar Echinococcosis (AE) seen at the specialized treatment unit in Ulm between January 1992 and December 2011 were included in the database. Follow up ended on 31.12.2012. Cases were defined to the likelihood of diagnosis as a "possible", "probable" or "confirmed" case . Diagnosis of AE was based on clinical presentation, epidemiological history, pathognomonic imaging findings, specific laboratory results, such as immunodiagnosis or histopathological findings in resected/ biopsied specimens, and/or detection of nucleic acid sequences in such specimens. The location of the larval lesions and its spread at diagnosis was documented using the PNM classification. Treatment with benzimidazoles was followed the WHO-IWGE recommendations. Treatment efficacy was monitored by US examination and FDG-PET scan or MRI. To categorize each case at each visit the terms "cured", "stable" or "progressive" were used. Patients' data was assessed at each visit; missing information was obtained from hospital records or the family doctor. Names were anonymized and data was stored in a Microsoft Excel database. Statistics were done with SAS version 9.3.

The data were stratified into series A containing diagnoses until December 1999 and series B from January 2000 onwards. This separation was chosen as patient admissions to the clinic rose almost 3-fold in 2000 when notification of AE became mandatory in Germany. It can be assumed that series B better represents AE patient characteristics, disease manifestation and comprehensive management; series A includes case histories with favorable prognoses at the time of diagnosis while optimal treatment for AE was still unavailable.

Outcome parameters for this study population were: overall survival after diagnosis, relapse after surgery or progression of remaining liver lesions in size or new lesions in other organs, and time to relapse or progress. Survival was estimated by the Kaplan Meier method.

Parameters with an assumed influence on the time until relapse or progress of the parasitic lesions entered Kaplan Meier survival analysis and Cox proportional hazard regression model analysis, respectively, and hazard ratios (HR) with corresponding 95% confidence intervals (CI) were calculated. Logistic regression was used to identify factors which may predict a successful treatment interruption using the odds ratio (OR) as an appropriate outcome parameter.