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

Abstract

Purpose: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Keywords: 18F-DCFBC; Biochemical recurrence; PSMA; PSMA-based PET imaging; Prostate cancer.

Conflict of interest statement

Conflict of interest Authors have no conflict of interest.

Figures

Fig. 1

18F–DCFBC PET/CT imaging and mpMRI demonstrating recurrent malignancy at the prostatectomy bed: 71-year-old man, with history of prostate cancer, Gleason 7 (4 + 3), status post-prostatectomy, with pre-scan PSA of 0.86 mg/mL. 18F–DCFBC axial fused PET/CT (a), and PET (b) images demonstrate a focus of abnormal DCFBC uptake at the prostatectomy bed (arrows), which was concordant with MR imaging findings, as seen on T2W MRI (c), ADC map (d) and DCE RMI (e); tumor recurrence was confirmed by biopsy, and patient started hormone therapy

Fig. 2

18F–DCFBC PET/CT imaging and mpMRI demonstrating seminal vesicles involvement years after radical prostatectomy: 60-year-old man, with history of prostate cancer, Gleason 7 (4 + 3), status post radical prostatectomy 10 years ago, with pre-scan PSA of 4.7 mg/mL. 18F–DCFBC PET (A1, A2) images demonstrate focal abnormal DCFBC in the bilateral seminal vesicles (arrows), concordant with the MR imaging findings, as seen on T2W MRI (B1, B2), ADC map (C) and b=2000 s/mm2 DW RMI (D); tumor recurrence was confirmed by biopsy, and seminal vesicles surgical resection was performed

Fig. 3

a. ROC analysis performed for surgical patients (n = 59) to assess the ability of pre-scan PSA in distinguishing between 18F–DCFBC PET/ CT positive and negative result, with an AUC (area under the operating characteristic curve) of 76.4%. b. The optimal cut-off pre-scan PSA, which maximizes the difference between the true-positive rate (TPR) and the false-positive-rate (FPR), was 0.78 ng/mL, i.e., at pre-scan PSA of 0.78 ng/mL, TPR was 87.5% (28/32) and FPR was 33.3% (9/27)

Fig. 4

18F-DCFBC PET/CT imaging demonstrating nodal involvement: 61-year-old male, with history of prostate cancer, Gleason 7, status postprostatectomy 2 years ago, with pre-scan PSA of 1.31 mg/mL. 18F–DCFBC fused PET/CT (top) and PET (bottom) images demonstrate two small 9 mm and 7 mm left paraaortic lymph nodes (arrows); biopsy confirmed tumor recurrence. Patient started treatment with enzalutamide.