Predicting Treatment Response in Primary Aldosteronism Using 11C-Metomidate Positron Emission Tomography

<jats:sec> <jats:title>Background</jats:title> <jats:p>Appropriate treatment of primary aldosteronism (PA) depends on accurate lateralization. <jats:sup>11</jats:sup>C-metomidate (MTO) is a tracer used in PET that provides functional information about the adrenal cortex. We aimed to perform MTO PET for patients with PA who are managed according to the guideline and to verify its correlation with other lateralization modalities and usefulness in outcome prediction.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>Seventeen patients with PA who underwent MTO PET and had ≥1 lateralization modality (adrenal venous sampling and/or NP-59 adrenal scintigraphy) were included. SUV<jats:sub>max</jats:sub> of each adrenal gland (higher uptake side, HSUV<jats:sub>max</jats:sub>; lower uptake side, LSUV<jats:sub>max</jats:sub>) and the ratio of HSUV<jats:sub>max</jats:sub> to LSUV<jats:sub>max</jats:sub> (contrast) were compared with lateralization modalities, postsurgical outcomes, and medical treatment outcomes. Cutoff values were used as outcome predictors.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>HSUV<jats:sub>max</jats:sub> and LSUV<jats:sub>max</jats:sub> increased in the order of bilateral, unilateral, and negative findings of CT, with opposite order of contrast. High discordant rate between MTO PET and other lateralization modalities was noted. Biochemical responders (n = 8) had significantly lower HSUV<jats:sub>max</jats:sub> and LSUV<jats:sub>max</jats:sub> than nonresponders, and clinical responders (n = 6) had borderline lower HSUV<jats:sub>max</jats:sub> than nonresponders. By optimal cutoff values of HSUV<jats:sub>max</jats:sub> and LSUV<jats:sub>max</jats:sub>, MTO PET was able to predict biochemical and clinical outcomes in patients with medical treatment.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusion</jats:title> <jats:p>According to adrenal CT findings, MTO PET presented different uptake patterns. Patients with PA under medical treatment showed significantly lower tracer uptake in responders. Thus, MTO PET may be a useful imaging biomarker to predict medical treatment outcome. Multicenter prospective study with a larger number of patients is needed for further validation.</jats:p> </jats:sec>