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

Appropriate treatment of primary aldosteronism (PA) depends on accurate lateralization. 11 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.

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 max of each adrenal gland (higher uptake side, HSUV max ; lower uptake side, LSUV max ) and the ratio of HSUV max to LSUV max (contrast) were compared with lateralization modalities, postsurgical outcomes, and medical treatment outcomes. Cutoff values were used as outcome predictors.

HSUV max and LSUV max 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 max and LSUV max than nonresponders, and clinical responders (n = 6) had borderline lower HSUV max than nonresponders. By optimal cutoff values of HSUV max and LSUV max , MTO PET was able to predict biochemical and clinical outcomes in patients with medical treatment.

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.