Clinical impact of PSMA-based ¹⁸F-DCFBC PET/CT imaging in patients with biochemically recurrent prostate cancer after primary local therapy.

Abstract

The purpose of our study was to assess ¹⁸F-DCFBC PET/CT, a PSMA targeted PET agent, for lesion detection and clinical management of biochemical relapse in prostate cancer patients after primary treatment. This is a prospective IRB-approved study of 68 patients with documented biochemical recurrence after primary local therapy consisting of radical prostatectomy (n = 50), post radiation therapy (n = 9) or both (n = 9), with negative conventional imaging. All 68 patients underwent whole-body ¹⁸F-DCFBC PET/CT, and 62 also underwent mpMRI within one month. Lesion detection with ¹⁸F-DCFBC was correlated with mpMRI findings and pre-scan PSA levels. The impact of ¹⁸F-DCFBC PET/CT on clinical management and treatment decisions was established after 6 months' patient clinical follow-up. Forty-one patients (60.3%) showed at least one positive ¹⁸F-DCFBC lesion, for a total of 79 lesions, 30 in the prostate bed, 39 in lymph nodes, and ten in distant sites. Tumor recurrence was confirmed by either biopsy (13/41 pts), serial CT/MRI (8/41) or clinical follow-up (15/41); there was no confirmation in five patients, who continue to be observed. The ¹⁸F-DCFBC and mpMRI findings were concordant in 39 lesions (49.4%), and discordant in 40 lesions (50.6%); the majority (n = 32/40) of the latter occurring because the recurrence was located outside the mpMRI field of view. ¹⁸F-DCFBC PET positivity rates correlated with PSA values and 15%, 46%, 83%, and 77% were seen in patients with PSA values <0.5, 0.5 to <1.0, 1.0 to <2.0, and ≥2.0 ng/mL, respectively. The optimal cut-off PSA value to predict a positive ¹⁸F-DCFBC scan was 0.78 ng/mL (AUC = 0.764). A change in clinical management occurred in 51.2% (21/41) of patients with a positive ¹⁸F-DCFBC result, generally characterized by starting a new treatment in 19 patients or changing the treatment plan in two patients. ¹⁸F-DCFBC detects recurrences in 60.3% of a population of patients with biochemical recurrence, but results are dependent on PSA levels. Above a threshold PSA value of 0.78 ng/mL, ¹⁸F-DCFBC was able to identify recurrence with high reliability. Positive ¹⁸F-DCFBC PET imaging led clinicians to change treatment strategy in 51.2% of patients.