Differentiating benign and malignant pancreatic masses: Ga-68 PSMA PET/CT as a new diagnostic avenue

Differentiation of malignant and benign pancreatic lesions on anatomical imaging is difficult in some cases with overlapping features. Prostate-specific membrane antigen (PSMA) is overexpressed during angioneogenesis in many tumors. We aimed to evaluate the PSMA expression in pancreatic lesions to differentiate these lesions and explore the performance of Ga-68 PSMA-PET/CT vis-a-vis F-18 FDG-PET/CT.

Patients with pancreatic lesions on conventional imaging were prospectively recruited. All the patients underwent a whole-body F-18 FDG-PET/CT and a regional abdominal Ga-68 PSMA-PET/CT. Focal tracer uptake (FDG or PSMA) on PET images was considered positive. Histopathology and/or cytopathology were considered the reference standard.

A total of forty patients (27 males, mean age 55.3 ± 9.8, range 37-71 years) were enrolled. Of these, 19 were diagnosed as malignant on histopathology/cytology. Patients with benign lesions showed no worsening of symptoms for at least 6 months on follow-up. FDG-PET/CT revealed 17 true-positive (TP), 9 false-positive (FP), 12 true-negative (TN), and 2 false-negative (FN) findings, whereas PSMA-PET/CT had 18 TP, 2 FP, 19 TN, and 1 FN finding. The sensitivity, specificity, PPV, NPV, and accuracy for FDG-PET/CT were 89.5%, 57.1%, 65.4%, 85.7%, and 72.5%, respectively, while for PSMA-PET/CT were 94.7%, 90.5%, 90%, 95%, and 92.5%, respectively. ROC curve analysis showed that the SUVmax value of 4.8 on PSMA-PET/CT could predict the malignant potential of a lesion with a specificity of 90.5% and a sensitivity of 84.2%.

Ga-68 PSMA-PET/CT imaging helped in establishing a non-invasive pre-operative diagnosis of primary pancreatic malignancy with a higher degree of specificity and accuracy compared with FDG-PET/CT.

• Conventional imaging such as CT and MRI are unable to reliably differentiate localized malignant pancreatic lesion from benign lesions mimicking malignancy such as mass-forming pancreatitis. • FDG PET/CT helps in detecting malignant foci in view of their increased glucose metabolism. However, it may be falsely positive in inflammatory lesions which may occasionally hinder its ability to differentiate between benign and malignant lesions. • Apart from prostatic malignancy, PSMA is overexpressed in neovasculature of many non-prostatic malignancies. The present study highlights that Ga68 PSMA PET/CT performed better in diagnosing malignancy non-invasively than FDG-PET/CT with a higher PPV (90.5% vs. 65.4%) and accuracy (92.5% vs. 72.5%).