18F-Fluciclovine-Avid Pulmonary Hamartoma

Abstract

A 73-year-old man with history of grade group 1/Gleason 3 + 3 = 6 prostate adenocarcinoma status post prostatectomy had subsequent biochemical recurrence with serum prostate-specific antigen level of 2.4 ng/mL. He underwent an 18F-fluciclovine PET/CT scan that demonstrated a left prostate bed recurrence and an incidental 18F-fluciclovine-avid smooth-edged solitary lung nodule with internal fat attenuation. Such uptake of 18F-fluciclovine in a lung hamartoma could be mistaken for prostate cancer metastasis. Given the increasing use of advanced imaging for prostate cancer, there is need for the imaging specialist to know about pitfalls and how to interpret them.

FIGURE 1.

A 73-year-old man with history prostate cancer was referred for ¹⁸F-fluciclovine PET/CT due to biochemical recurrence. He had initially been diagnosed with prostate adenocarcinoma, pT2N0M0 grade group 1/Gleason 3 + 3 = 6, after undergoing radical retropubic prostatectomy and bilateral pelvic lymphadenectomy in 2008. He also received androgen deprivation therapy. By the time of imaging, his serum prostate-specific antigen had gradually risen to 2.4 ng/mL. A, MIP image demonstrating a subtle focus of ¹⁸F-fluciclovine in the left prostate bed along a surgical clip, concerning for locally recurrent prostate disease (black arrow). In addition, there is an incidental ¹⁸F-fluciclovine–avid left upper lobe pulmonary nodule (dashed arrow). B, Axial CT image without IV contrast depicting the left prostatectomy clip (white arrow). C, Same slice axial PET image demonstrating a focus of ¹⁸F-fluciclovine with SUV_max of 2.3 (black arrow). D, Same slice fused axial PET/CT images demonstrate the ¹⁸F-fluciclovine uptake at the same level (white arrow).

FIGURE 2.

A, Axial CT image without IV contrast depicting the smoothly outlined fat-containing left upper lobe pulmonary nodule, consistent with a hamartoma (white arrow). B, Same slice axial CT image with lung window (black arrow). C, Same slice axial PET image demonstrating ¹⁸F-fluciclovine avidity with SUV_max of 2.3 (black dashed arrow). D, Same slice fused axial PET/CT images in grayscale demonstrate the ¹⁸F-fluciclovine uptake at the same level (white dashed arrow). ¹⁸F-fluciclovine is a US Food and Drug Administration–approved agent indicated for men with suspected recurrent prostate cancer. This agent had initially been studied in cerebral gliomas and may have utility in other cancer types, suggesting that interpretation of ¹⁸F-fluciclovine for men with prostate cancer can have important pitfalls and incidental findings. Metastatic spread of prostate cancer to the lung has been reported in approximately 46% of patients through hematogenous spread. In addition, there is a small molecular subset of prostate cancers that metastasize exclusively to the lung. With the increased use of advanced imaging for prostate cancer (¹⁸F-fluciclovine, ⁶⁸Ga-PSMA-11, ¹⁸F-DCFPyL, etc), there is a need for imaging specialists to know about pitfalls and how to avoid and interpret them.^, It is important to exclude extrapelvic disease when interpreting an ¹⁸F-fluciclovine scan, as that can be an important determining factor in planning out treatment for recurrent prostate cancer. In addition, the interpreting imaging specialist needs to look carefully at the correlative CT imaging to avoid a false-positive interpretation. In a pilot study, there was no significant difference in SUV_max between malignant and inflammatory pulmonary lesions with ¹⁸F-fluciclovine. In this case, the lung hamartoma is smoothly outlined with localized spherical fat. Differentiating a benign pulmonary nodule such as this hamartoma based on CT characteristics is of clinical importance to avoid unnecessary future tests and procedures,^, as well as to ensure patients remain candidates for potential curative therapies such as salvage pelvic radiation.