Pituitary Adenoma on 18F-Fluciclovine PET/CT

18F-Fluciclovine Uptake in Intramuscular Injecting Site of Antiandrogen

ABSTRACT

18F-fluciclovine, a radiolabeled amino acid analog, has been approved by US Food and Drug Administration for detecting lesions of biochemical recurrence of prostate adenocarcinoma with PET/CT. However, it is not specific for prostate cancer and has been found to be present in variety of malignant and benign etiologies. We herein present an interesting case of the incidental finding of increasing uptake of 18F-fluciclovine related to intramuscular injection of antiandrogen.

Incidental Uptake of 18F-Fluciclovine by Type AB Thymoma

ABSTRACT

Biochemical recurrence of prostate cancer, detected by a rising PSA, may reflect intraprostatic or extraprostatic recurrence. 18F-Fluciclovine (Axumin), a synthetic amino acid substrate in tumor metabolism, has frequently been used for to localize recurrent prostate cancers. We present a 71-year-old man with biochemical recurrence of prostate cancer but no convincing imaging findings on 18F-fluciclovine PET/CT. Of note, however, was an incidental uptake within the anterior mediastinum, which was found on biopsy to be a type AB thymoma. With this, we stress that awareness of false-positive uptake patterns is crucial for accurate diagnosis of recurrent prostate cancer.

Papillary Urothelial Carcinoma of Urinary Bladder Identified on 18F-Fluciclovine PET/CT

ABSTRACT

18F-fluciclovine is a radiolabeled synthetic amino acid recently approved by the Food and Drug Administration for evaluating recurrent prostate cancer. Upregulated amino acid transporters in prostate cancer cells result in elevated radiotracer uptake in sites of tumor recurrence. However, 18F-fluciclovine is not specific for prostate cancer. Nonprostatic malignancies and benign conditions can also demonstrate uptake. This information combined with the knowledge about common patterns of prostate cancer recurrence helps guide appropriate management. We present an 87-year-old man with biochemical recurrence for prostate cancer but found to have a urinary bladder wall mass on 18F-fluciclovine PET/CT with moderate avidity. Biopsy revealed papillary urothelial carcinoma.

Gastrointestinal Stromal Tumor Incidentally Detected on 18F-Fluciclovine PET/CT

ABSTRACT

We present a case of metastatic gastrointestinal stromal tumor incidentally detected on 18F-fluciclovine PET/CT. A 68-year-old man with history of intermediate-risk prostate cancer (Gleason score 4 + 3 = 7; pT2cN0M0) previously treated with retropubic radical prostatectomy, adjuvant whole pelvis radiation, and androgen deprivation therapy (leuprolide) presented with slowly rising serum prostate-specific antigen over 3 years, concerning for recurrent prostate cancer. To identify potential sites of recurrent disease, an 18F-fluciclovine PET/CT was obtained. Multiple tracer-avid mesenteric masses and enlarged lymph nodes were found throughout the abdomen and pelvis, later biopsy-proven to reflect metastatic gastrointestinal stromal tumor.

Synchronous Malignancies Identified by 18F-fluciclovine Positron Emission Tomography for Prostate Cancer: Case Series and Mini-Review

Positron emission tomography using the fluorine-18 (¹⁸F) fluciclovine radiotracer has been approved for use in recurrent prostate cancer and is a useful tool for clinical decision making. However, ¹⁸F-fluciclovine is not specific for prostate cancer tumor cells, and false-positive results have been reported. In the present study, we have reported our experience with synchronous malignancies identified using ¹⁸F-fluciclovine and reviewed other reported cases, with a special emphasis on highlighting the clinical decisions that led to the correct diagnosis.