Biochemical recurrence of prostate cancer, a pictorial comparison of 18F-PSMA and 18F-fluciclovine.

Introduction: Prostate cancer (PCa) is the most commonly diagnosed malignancy in men and the fifth leading cause of cancer deaths in this population. [1]. It is most commonly diagnosed in the elderly and has a strong association between mortality and increasing age. African Americans have a higher incidence and an increased risk for aggressive tumors [2].

Methods: This educational exhibit will review the applications of 18F-PSMA PET/CT (PSMA) and 18F-fluciclovine PET/CT (Axumin), agents in patients with biochemical recurrence of PCa. It will be based on direct case-based comparisons of PSMA and Axumin studies performed 1 month apart in patients with biochemical recurrence of PCa.

Results: Evaluation of PCa typically requires multimodality imaging including computed tomography (CT), magnetic resonance imaging (MRI), and bone scintigraphy. In recent years, positron emission tomography (PET-CT) has gained increasing use for the evaluation of PCa, particularly in indolent disease ^[3]. PSMA and Axumin are among the most common radiopharmaceuticals for PET imaging ^[4].

In 2016, Axumin was approved by the FDA for evaluation of suspected recurrent of PCa. The advantage of using this radiotracer stems from the increased amino acid transport into PCa cells. It provided a higher sensitivity than most other modalities available at the time for detection of recurrent and metastatic disease ^[5]. Since its approval in 2021, PSMA is quickly expanding and replacing Axumin for both primary and recurrent cancer evaluation.

For evaluation of localized disease, PSMA has shown a higher sensitivity compared to MRI, and other PET radiopharmaceuticals including ¹¹C-Choline and Axumin. It has an increasing role in treatment management strategy by allowing detection of smaller metastatic lesions isolating patients in need of radiotherapy and narrowing the radiation treatment fields ^[4]. One study demonstrated greater detection rate of biochemically recurrent PCa compared to Axumin[10].

On the other hand, some studies have found no statistically significant difference between PSMA and Axumin in their ability to detect primary PCa and local extension ^[8]. A prospective study by Pernthaler in 58 patients with biochemical recurrence of PCa demonstrated an advantage in Axumin for detecting curable localized disease in close anatomical relation to the urinary bladder, whereas PSMA limited due to intense activity in the urinary bladder [9]. However, some centers have begun using furosemide for evaluation of the prostate bed in PSMA studies [11].

Conclusions: Axumin and PSMA are well-known and proven modalities for evaluating primary PCa and its local extension. With satisfactory diagnostic accuracy and increased detection rates with respect to conventional imaging modalities, PET may provide substantial clinical impact in disease management. Thus, for initial evaluation of primary prostatic tumor, Axumin and PSMA could serve as accurate imaging modalities that might benefit the management of patients with high-risk PCa. PSMA has demonstrated some advantages over Axumin, including a higher detection rate of biochemical recurrence.