Non-Prostate Cancer Tumours: Incidence on 18f-Dcfpyl Psma Pet/Ct and Psma Expression Characteristics in 1445 Patients.
Abstract PurposeProstate cancer (PCa) imaging has been revolutionized by Positron emission tomography (PET) tracers targeted to prostate specific membrane antigen (PSMA). Identification and characterization of non-PCa tumors has become an increasing clinical dilemma with growing use. The primary aim of this retrospective multicenter analysis was to determine atypical PSMA expression in PCa and expression in non-PCa tumors to aid providing clinically relevant reports and guiding multidisciplinary discussion.MethodsRetrospective multicenter study examining 1445 consecutive 18F-DCFPyL PSMA PET/CT between 2016-2020. Referrals were from public and private, secondary and tertiary referral centres serving New Zealand and Melbourne. Repeat studies were excluded. Lesions atypical for PCa were categorized into four groups: 1. Atypical PCa metastases 2. Non-PCa tumors 3. Benign and 4. Indeterminate.Results67 patients had lesions atypical for PCa metastases; 11.9% atypical prostate cancer metastases, 25.4% non-PCa tumors, 40.3% indeterminate, 10.4% benign. With the exception of Renal Cell Carcinoma (RCC), the non-PCa tumors, indeterminate and benign lesions demonstrated low PSMA expression. Most atypical PCa metastases demonstrated significant expression. Limitations included retrospective design and lack of histopathological correlation/follow up in some.Conclusions: Non-PCa tumor detection is low. Lesions demonstrating significant PSMA expression were almost exclusively PCa metastases. Differentiation of atypical PCa metastases from second primary malignancies is vital to avoid unnecessary investigation, delayed therapy and additional costs.