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

Esther Mena, Maria L. Lindenberg, Joanna H. Shih, Stephen Adler, Stephanie Harmon, Ethan Bergvall, Deborah Citrin, William Dahut, Anita T. Ton, Yolanda McKinney, Juanita Weaver, Philip Eclarinal, Alicia Forest, George Afari, Sibaprasad Bhattacharyya, Ronnie C. Mease, Maria J. Merino, Peter Pinto, Bradford J. Wood, Paula Jacobs, Martin G. Pomper, Peter L. Choyke, Baris Turkbey

The purpose of our study was to assess (18)F-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 (18)F-DCFBC PET/CT, and 62 also underwent mpMRI within one month. Lesion detection with (18)F-DCFBC was correlated with mpMRI findings and pre-scan PSA levels. The impact of (18)F-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 (18)F-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 (18)F-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. (18)F-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 (18)F-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 (18)F-DCFBC result, generally characterized by starting a new treatment in 19 patients or changing the treatment plan in two patients. (18)F-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, (18)F-DCFBC was able to identify recurrence with high reliability. Positive (18)F-DCFBC PET imaging led clinicians to change treatment strategy in 51.2% of patients.