High-sensitivity total-body 18F-fluciclovine PET/CT scans show promise in prostate cancer

Findings from a pilot study presented during the 2021 American Association for Radiation Oncology Annual Meeting suggested that high-sensitivity total-body PET/CT imaging using ¹⁸F-fluciclovine (Axumin) may have a “promising” role in patients with biochemically recurrent prostate cancer.¹

The investigators for the single-institution study found that detection rates “compared favorably to the published historical controls using fluciclovine or even PSMA on conventional PET/CT scanners.” They also noted that in the majority of patients, the study findings resulted in impactful changes to clinical management.

The synthetic amino acid radiopharmaceutical ¹⁸F-fluciclovine is approved by the FDA for the assessment of prostate cancer recurrence. “¹⁸F-fluciclovine may show modest lesion detectability rates on conventional PET/CT scanners, especially for low PSA levels (<30%),” the authors wrote. They launched this study to assess whether a total-body PET/CT scanner provides an enhanced capacity to detect lower disease burden.

The study took place at the University of California, Davis. Between December 2019 and February 2021, the prospective, IRB-approved study enrolled 21 patients with a history of prostate cancer. The median patient age was 69.7 ± 7.5 yrs. Prior therapy included prostatectomy (n = 18), external-beam radiation therapy (n = 2), and brachytherapy (n = 1). All patients had biochemical recurrence (American Urological Association criteria).

Following negative or equivocal cross-sectional conventional imaging, all 21 patients received standard ¹⁸F-fluciclovine total-body PET/CT scans. The PET/CT images were examined for suspicious recurrent or metastatic lesions. Rates of detection were calculated as percentage per PSA category. The suggested treatment approaches for each patient were recorded prior to and following ¹⁸F-fluciclovine PET/CT testing.

Overall, 71% (n = 15) of patients had detectable lesions. The lesion occurred in 24 locations, including 8 in the prostate bed/seminal vesicles, 7 N1 station, and 9 M1. The M1 lesions comprised 3 M1a, 1 M1b, and 5 M1c in different combinations.

The detection rates for each PSA category on a patient basis were: 2/4 (50%) for <0.2 ng/mL; 4/5 (80%) for 0.2-0.5 ng/mL; 2/4 (50%) for 0.51-1.00 ng/mL; 2/3 (67%) for 1.01-2.00 ng/mL; and 5/5 (100%) for >2.00 ng/mL.

“Overall, detection rate was 10/16 (63%) for PSA <2 ng/mL (compared to published rates of 26% for fluciclovine and 56%for PSMA),” the author wrote.

All but 3 patients (18/21; 87%) had a change in their clinical management. These included a switch to focal ablative radiation therapy in 62% (n = 13), systemic therapy in 10% (n = 2), and active surveillance in 5% (n = 1). The other 10% (n = 2) had a change in the systemic therapy they were already receiving.

The investigators noted in their conclusion that there is an ongoing larger study to validate these initial findings.

Reference

1. Azghadi S, Abdelhafez Y, Parikh M, et al. Detectability rates and impact on management from high-sensitivity total-body ¹⁸F-fluciclovine PET/CT scans in patients with prostate cancer biochemical recurrence. Int J Radia Oncol Biol Phys. 2021;111(suppl 3):S1. doi: 10.1016/j.ijrobp.2021.07.867