Prognostic Utility of (18)F-Fluciclovine Positron Emission Tomography (FACBC) in Biochemically Recurrent (BCR) Prostate Cancer (PCa) Treated with Salvage Radiotherapy

Abstract

<h3>Purpose/Objective(s)</h3> Patients with a biochemical recurrence after definitive radiotherapy or prostatectomy often undergo imaging to localize recurrent disease prior to salvage treatment. FACBC is a commonly utilized scan for this, but little is known about the prognostic utility of imaging metrics derived from FACBC scans in this setting. <h3>Materials/Methods</h3> This single-center retrospective study included 167 patients (pts) who had FACBC for BCR between 10/2017-10/2019. Clinical, pathological, imaging, and treatment data were collected by chart review. Pts who received salvage radiotherapy (SRT) were then identified and classified by whether their scan was positive or negative. Imaging metrics derived from positive scans included maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion metabolism (TLM). Freedom from biochemical progression (FFBP) and overall survival (OS) were compared between pts with positive and negative scans according to the Kaplan-Meier method, and for the above imaging metrics dividing each metric by its median value. Cox regression analysis for the following covariates was also performed: number of recurrence sites, SUVmax, MTV, and TLM. <h3>Results</h3> 71 pts received SRT; 34 had positive scans. The median FFBP for all patients who received SRT was 130 weeks (range 58.4-244.9). There was a statistical difference in FFBP between patients with negative and positive scans (median 130 vs. 128 weeks, p=0.039), but no difference in OS (median 130 vs. 146 weeks, p = 0.140). Among pts with positive scans, there was no difference in FFBP when considering high vs. low SUVmax, MTV, or TLF. There was also no difference when these factors were analyzed via cox regression. <h3>Conclusion</h3> In this retrospective cohort of 71 pts with FACBC PET scans treated with SRT, pts with a negative FACBC had a longer time to biochemical progression, but this did not affect overall survival. Although SUVmax, MTV, and TLM have been shown to be prognostic in other cancers with other PET tracers, none were prognostic in this cohort.