Correlation between imaging features and rEm18 antibodies in alveolar echinococcosis: results from a multicenter study in France

Background: To correlate imaging features of alveolar echinococcosis (AE) with the antibodies to recombinant Em18 (rEm18AB) at diagnosis and evaluate initial imaging features associated with serologic response, this retrospective study used data from the prospective multicenter EchinoVISTA study (NCT02876146). Imaging and serology were performed at diagnosis and during follow-up. Univariate and multivariate analyses were used to evaluate imaging features associated with the rEm18AB index. Follow-up analyses evaluated the imaging features associated with serologic response (defined as a 50% reduction in the baseline value within 2 years) in non-operated patients treated with albendazole alone. Results: From June 2012 to July 2016, 45 patients were included, with 8/45 (18%) having an rEm18AB index < 1. Maximum lesion size (76 mm [IQR = 57–93] vs. 36 mm [IQR = 26–51], p = 0.006), microcyst percentage (70% [IQR = 3–8] vs. 20% [IQR = 0.5–3.5], p = 0.004), and maximum standardized uptake value (SUV) on fluorodeoxyglucose positron emission tomography (5.1 [IQR = 4.4–6.2] vs. 2.6 [IQR = 2.4–3.9], p = 0.001) were associated with an rEm18AB index > 1. In patients treated with albendazole, serologic responders at 2 years had smaller lesions (5.3 [IQR = 3.8–72] vs. 3.5 [IQR = 2.7–3.7], p = 0.010) with less pedicle involvement, and lower initial rEm18AB index (2.98 ± 1.63 vs. 7.81 ± 3.95, p = 0.011). Conclusion: Maximum lesion size, percentage of microcysts within the lesion, and maximum lesion SUV are significant imaging features of AE correlated with the rEm18AB index. Serologic response at 2 years occurs primarily in patients with small lesions and a low rEm18AB index.