Non-prostate cancer malignancies detected by 18F-Fluciclovine PET/CT.

Abstract

Listen

Translate article

28 Background: Novel imaging modalities such as 18F-fluciclovine PET/CT provide additional sensitivity over conventional imaging modalities in the workup of recurrent prostate cancer (PC). The range of published sensitivity and specificity values for 18F-fluciclovine is broad, however, and NCCN guidelines note the scan’s high false-positive rate. Prior case reports have described incidental detection of non-PC using this modality, including melanoma, oropharyngeal, pancreatic, penile, liver, and breast cancers. Herein, we surveyed our institutional 18F-fluciclovine PET/CT results to assess the rate and histologies of incidentally-detected non-PC. Methods: We retrospectively identified consecutive men with PC who underwent 18F-fluciclovine PET/CT as part of their disease workup. After identifying studies with unequivocal PET-avidity, we assessed for subsequent tissue sampling and/or imaging to confirm a non-PC malignancy. We report these patients’ clinicopathologic data. Results: Three-hundred thirty-six men underwent 18F-fluciclovine PET/CT for PC at our institution between 6/2017-7/2019. Seven (2%) were found to have non-PC malignancies. The diagnoses were: meningioma (n=3, 43%), non-small cell lung cancer (NSCLC) (n=2, 29%), gastric adenocarcinoma (n=1, 14%), and pancreatic neuroendocrine tumor (n=1, 14%). One of the patients with meningioma underwent resection as a result, while the other two were surveilled by MRI. Both cases of NSCLC were biopsied and resected. Tissue sampling was not performed in the gastric or pancreatic cases, as these patients were already known to have these malignancies. Conclusions: In this large institutional series, we found a low rate (2%) yet broad range of non-PC malignancies incidentally detected by 18F-fluciclovine PET/CT performed for PC, including diagnoses not previously reported in the literature. Such detection allowed patients to receive definitive management or appropriate surveillance for the non-PC malignancies. These findings underscore the importance of clinical and/or pathological correlation of positive scan results.