⁶⁸Ga-pentixafor PET pulmonary uptake in patients with suspected primary aldosteronism: incidence and etiology

Background: We have incidentally noted focal pulmonary uptake in a cohort of our patients with suspected primary aldosteronism (PA) on ⁶⁸Ga-pentixafor positron emission tomography/computed tomography (PET/CT) or positron emission tomography/magnetic resonance (PET/MR) images. We aimed to assess the incidence and possible etiology of pulmonary uptake in these patients.

Methods: There were 217 consecutive suspected PA patients referred for ⁶⁸Ga-pentixafor PET/CT or PET/MR retrospectively reviewed. The presence or absence of pulmonary uptake was recorded. Clinical and PET-related parameters were collected. Modality-based analyses were performed to evaluate pulmonary uptake incidence and blood-pool standardized uptake value (SUV) measurements between PET/CT and PET/MR. Among patients with pulmonary uptake, the highest pulmonary maximum standardized uptake value (SUVmax) and blood pool (BP) normalized highest pulmonary SUVmax were also compared descriptively between modalities.

Results: Pulmonary uptake was present in 37 of 217 patients (17%). The incidence of pulmonary uptake did not significantly differ between PET/CT and PET/MR groups (1/11, 9.1% vs. 36/206, 17.5%; P=0.695), and BP SUVmax and mean standardized uptake value (SUVmean) were also comparable between PET/CT and PET/MR groups (SUVmax: median, 2.99 vs. 2.68, P=0.075; SUVmean: median, 2.03 vs. 2.02, P=0.799). Among patients with pulmonary uptake, lesion-level SUV comparison was descriptive because only one patient underwent PET/CT; the highest pulmonary SUVmax and BP normalized highest pulmonary SUVmax were 8.15 and 4.20 in this patient, compared with median values of 4.25 and 2.07 in PET/MR patients, respectively. Among all clinical and PET-related parameters, only elevated leukocyte and neutrophil counts were observed to be significantly associated with pulmonary uptake (25.9% vs. 1.8%, P<0.001). Among patients with available laboratory data, the highest pulmonary SUVmax was not significantly correlated with absolute neutrophil count (Spearman r=−0.250, P=0.208) or leukocyte count (Spearman r=−0.283, P=0.153). In patients with uptake, median SUVmax showed no significant difference between left and right lungs (3.71 vs. 3.76, P=0.473). Additionally, no significant difference was observed between lower and upper lung fields (47% vs. 49%, P>0.99). Of these 37 patients, 20 patients had recent chest computed tomography (CT) scan. Abnormality was noted in one patient, who had subpleural linear opacity in the corresponding area.

Conclusions: Pulmonary uptake was observed in approximately one-sixth of suspected PA patients undergoing ⁶⁸Ga-pentixafor scans. Our findings suggest that pulmonary uptake on ⁶⁸Ga-pentixafor scans may be associated with potential inflammation.