Is There Any Role for ¹⁸F-Fluciclovine PET/CT in the Presence of Undetectable PSA in Prostate Cancer Patients After Definitive Treatment?

Purpose The aim of this study was to investigate the role of 18F-fluciclovine PET/CT in the evaluation of prostate cancer (PC) patients after definitive treatment in the presence of undetectable prostate-specific antigen (PSA). Patients and Methods This retrospective study was conducted in PC patients who had undetectable PSA level and underwent fluciclovine PET/CT within a 2-week interval of PSA examination and without interval treatment or other cancer. Patient and tumor characteristics at initial diagnosis, treatment regimens, and findings on fluciclovine PET/CT were collected. Comparisons between groups of positive and negative fluciclovine PET/CT were done by using descriptive statistics. Results A total of 34 fluciclovine PET/CTs from 34 patients met the inclusion criteria. There were 4 positive (11.8%) and 30 negative fluciclovine PET/CTs (88.2%). All of the patients with positive results had an initial Gleason score of 7 or higher and locally advanced tumor (T3-T4). More common features at the time of diagnosis among positive study patients as compared with negative ones were atypical histologic variants (25% vs 0%) and very high-risk PC (50% vs 30%). Most of the patients with positive study received second-line hormonal therapy (HT) (50%), whereas patients with negative results received first-line HT (53.3%). Chemotherapy naivety was less common among positive patients (75% vs 96.7%). Sites of involvement on positive fluciclovine PET/CTs were pelvic lymph nodes (2/4, 50%), lung and mediastinal lymph node (1/4, 25%), and prostatectomy bed (1/4, 25%). Conclusions In the presence of undetectable PSA in PC patients after definitive treatment, fluciclovine PET/CT would benefit most to patients with Gleason score of 7 or higher, high disease burden (T3-T4), and atypical histologic variants at the time of diagnosis, and the ones who have history of second-line HT and/or chemotherapy.