Study assesses clinical value of FACBC PET/CT imaging in prostate cancer

Findings from a retrospective review of men who underwent ¹⁸F-fluciclovine (FACBC) PET/CT imaging for biochemically recurrent prostate cancer following curative intent local therapy provide real world insight into its performance characteristics and impact on treatment management, reported investigators from the University of North Carolina, Chapel Hill.¹

Their single-center study included 103 men, of whom 77 (75%) had lesions consistent with prostate cancer recurrence detected by FACBC PET/CT. The sites identified by the imaging most commonly occurred outside the pelvis (48%).

Stratification of men based on prostate-specific antigen (PSA) showed the likelihood of having a positive FACBC PET/CT increased with increasing PSA level. Yet recurrent disease was detected in more than one-third of men with a PSA less than 1 ng/mL.

The clinical impact of the imaging was assessed in a subgroup of 34 men post prostatectomy who had undergone conventional imaging. Within this cohort, 15 men (44%) had a change in recommended radiotherapy based on the findings from FACBC PET/CT imaging; the recommendation was to increase the dose in 11 men and was changed from treatment to palliative therapy in 4 men.

“FACBC PET/CT imaging for staging biochemically recurrent prostate cancer is endorsed by national guidelines, but there are limited studies investigating its performance and how its findings may affect treatment decision-making,” said Marc A. Bjurlin, DO, MSc, associate professor of urology, University of North Carolina.

“Our study further defines the performance characteristics of FACBC PET/CT imaging and supports its use for evaluating men with biochemically recurrent prostate cancer, even at low PSA thresholds,” Bjurlin added.

Of the 103 men in the study, 64 had undergone prostatectomy with curative intent and 37 were patients post radiation. The FACBC PET/CT detection rate was similar in the 2 groups. Median PSA for the entire cohort at the time of FACBC PET/CT imaging was 2.7 ng/mL (range, 0-67.4 ng/mL) and was less than 1 ng/mL in 31 men, 1 to less than 2 ng/mL in 11 men, and greater than 2 ng/mL in 61 men. The FACBC PET/CT positivity rates in the 3 PSA subgroups were 35.5%, 63.6%, and 96.7%, respectively. Among men with a PSA less than 1 mg/mL, the detected site of involvement was extraprostatic/extrapelvic in 45.5%.

Recurrent disease can be detected at low PSA thresholds

“These results highlight that in men with suspected biochemically recurrent prostate cancer, FACBC PET/CT can detect recurrent disease at low PSA thresholds. Utilizing a lower PSA threshold of 1.0 ng/mL as the trigger for this imaging may allow recurrent disease to be identified early while disease remains in an oligometastatic state and salvage interventions may remain an option,” Bjurlin said.

He continued, “Considering that recurrence outside of the pelvis was so common in our series, future studies may consider investigating a role for extending whole pelvis radiation therapy volumes to increase coverage of superior nodal regions. Additionally, patients may benefit from investigation of metastasis-directed therapies, including stereotactic ablative radiotherapy to treat nodal disease. The emerging fields of radiomics and radiogenomics could provide important prognostic information and aid decision making for patients with recurrent prostate cancer.”

In December 2020, the FDA approved Gallium 68 PSMA-11 for imaging in men with suspected prostate cancer metastasis who are potentially curable through surgery or radiation therapy and for those with suspected recurrence based on an elevated PSA level.

“Compared with FACBC, Gallium 68 PSMA-11 appears to further increase the detection of metastatic disease and can impact patient management. We are now studying the performance characteristics of this new radiotracer at our institution,” Bjurlin said.

Bjurlin acknowledged Jamie Michael, BS, University of North Carolina medical student and first author of the published article, for drafting the paper.

Reference

1. Michael J, Khandani AH, Basak R, et al. Patterns of recurrence, detection rates, and impact of 18-F Fluciclovine PET/CT on the management of men with recurrent prostate cancer. Urology. Published online January 29, 2021. doi:10.1016/j.urology.2021.01.038